Developmental nicotine exposure affects larval brain size and the adult dopaminergic system of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Background

Pregnant women may be exposed to nicotine if they smoke or use tobacco products, nicotine replacement therapy, or via e-cigarettes. Prenatal nicotine exposure has been shown to have deleterious effects on the nervous system in mammals including changes in brain size and in the dopaminergic system. The genetic and molecular mechanisms for these changes are not well understood. A Drosophila melanogaster model for these effects of nicotine exposure could contribute to faster identification of genes and molecular pathways underlying these effects. The purpose of this study was to determine if developmental nicotine exposure affects the nervous system of Drosophila melanogaster, focusing on changes to brain size and the dopaminergic system at two developmental stages.

Results

We reared flies on control or nicotine food from egg to 3rd instar larvae or from egg to adult and determined effectiveness of the nicotine treatment. We used immunohistochemistry to visualize the whole brain and dopaminergic neurons, using tyrosine hydroxylase as the marker. We measured brain area, tyrosine hydroxylase fluorescence, and counted the number of dopaminergic neurons in brain clusters.We detected an increase in larval brain hemisphere area, a decrease in tyrosine hydroxylase fluorescence in adult central brains, and a decrease in the number of neurons in the PPM3 adult dopaminergic cluster. We tested involvement of Dα7, one of the nicotinic acetylcholine receptor subunits, and found it was involved in eclosion, as previously described, but not involved in brain size.

Conclusions

We conclude that developmental nicotine exposure in Drosophila melanogaster affects brain size and the dopaminergic system. Prenatal nicotine exposure in mammals has also been shown to have effects on brain size and in the dopaminergic system. This study further establishes Drosophila melanogaster as model organism to study the effects of developmental nicotine exposure. The genetic and molecular tools available for Drosophila research will allow elucidation of the mechanisms underlying the effects of nicotine exposure during development.

     

Filamentous Aggregation of Sequestosome-1/p62 in Brain Neurons and Neuroepithelial Cells upon <Emphasis Type="Italic">Tyr-Cre</Emphasis>-Mediated Deletion of the Autophagy Gene <Emphasis Type="Italic">Atg7</Emphasis>

Defects in autophagy and the resulting deposition of protein aggregates have been implicated in aging and neurodegenerative diseases. While gene targeting in the mouse has facilitated the characterization of these processes in different types of neurons, potential roles of autophagy and accumulation of protein substrates in neuroepithelial cells have remained elusive. Here we report that Atg7^f/f Tyr-Cre mice, in which autophagy-related 7 (Atg7) is conditionally deleted under the control of the tyrosinase promoter, are a model for accumulations of the autophagy adapter and substrate sequestosome-1/p62 in both neuronal and neuroepithelial cells. In the brain of Atg7^f/f Tyr-Cre but not of fully autophagy competent control mice, p62 aggregates were present in sporadic neurons in the cortex and other brain regions as well in epithelial cells of the choroid plexus and the ependyma. Western blot analysis confirmed a dramatic increase of p62 abundance and formation of high-molecular weight species of p62 in the brain of Atg7^f/f Tyr-Cre mice relative to Atg7^f/f controls. Immuno-electron microscopy showed that p62 formed filamentous aggregates in neurons and ependymal cells. p62 aggregates were also highly abundant in the ciliary body in the eye. Atg7^f/f Tyr-Cre mice reached an age of more than 2 years although neurological defects manifesting in abnormal hindlimb clasping reflexes were evident in old mice. These results show that p62 filaments form in response to impaired autophagy in vivo and suggest that Atg7^f/f Tyr-Cre mice are a model useful to study the long-term effects of autophagy deficiency on the homeostasis of different neuroectoderm-derived cells.     

Anti-Müllerian hormone may regulate the number of calbindin-positive neurons in the sexually dimorphic nucleus of the preoptic area of male mice

Background

The male brain is putatively organised early in development by testosterone, with the sexually dimorphic nucleus of the medial preoptic area (SDN) a main exemplifier of this. However, pubescent neurogenesis occurs in the rat SDN, and the immature testes secrete anti-Müllerian hormone (AMH) as well as testosterone. We have therefore re-examined the development of the murine SDN to determine whether it is influenced by AMH and/or whether the number of calbindin-positive (calbindin^+ve) neurons in it changes after pre-pubescent development.

Methods

In mice, the SDN nucleus is defined by calbindin^+ve neurons (CALB-SDN). The number and size of the neurons in the CALB-SDN of male and female AMH null mutant (Amh ^-/- ) mice and their wild-type littermates (Amh ^+/+ ) were studied using stereological techniques. Groups of mice were examined immediately before the onset of puberty (20 days postnatal) and at adulthood (129–147 days old).

Results

The wild-type pre-pubertal male mice had 47% more calbindin^+ve neurons in the CALB-SDN than their female wild-type littermates. This sex difference was entirely absent in Amh ^-/- mice. In adults, the extent of sexual dimorphism almost doubled due to a net reduction in the number and size of calbindin^+ve neurons in females and a net increase in neuron number in males. These changes occurred to a similar extent in the Amh ^-/- and Amh ^+/+ mice. Consequently, the number of calbindin^+ve neurons in Amh ^-/- adult male mice was intermediate between Amh ^+/+ males and Amh ^+/+ females. The sex difference in the size of the neurons was predominantly generated by a female-specific atrophy after 20 days, independent of AMH.

Conclusions

The establishment of dimorphic cell number in the CALB-SDN of mice is biphasic, with each phase being subject to different regulation. The second phase of dimorphism is not dependent on the first phase having occurred as it was present in the Amh ^-/- male mice that have female-like numbers of calbindin^+ve neurons at 20 days. These observations extend emerging evidence that the organisation of highly dimorphic neuronal networks changes during puberty or afterwards. They also raise the possibility that cellular events attributed to the imprinting effects of testosterone are mediated by AMH.

     

<Emphasis Type="Italic">Agrobacterium rhizogenes</Emphasis> transformed calli of the holoparasitic plant <Emphasis Type="Italic">Phelipanche ramosa</Emphasis> maintain parasitic competence

Phelipanche and Orobanche spp. (broomrapes) are economically important parasitic weeds, causing severe damage to many agricultural crops. However, conventional methods to control these parasitic weeds are often not effective. Targeting molecular and biochemical processes involved in the establishment of the connection between the parasite and the host may offer a new perspective for control. However, progress in the understanding of these processes is hampered by the fact that genetic transformation and regeneration of these parasites is difficult if not impossible due to their specific lifecycle. Phelipanche and Orobanche spp. are holoparasites that need to attach to the roots of a host plant to get their assimilates, nutrients and water to develop and reproduce. The present study describes a highly efficient genetic transformation and regeneration protocol for the root holoparasitic Phelipanche ramosa. We present a new transformation system for P. ramosa using Agrobacterium rhizogenes MSU440 carrying a non-destructive selection marker gene coding for a red fluorescent protein (DsRed1). Using this protocol up to 90% transformation efficiency was obtained. We transformed 4 weeks old P. ramosa calli and transgenic calli expressing DsRed1 were then cultured on host plants. For the first time, we present shoot and flower development of the transgenic parasitic plant P. ramosa after successful connection of transgenic calli with the host plant roots. Moreover, we also present, for the first time, growth and development of P. ramosa shoots and flowers in vitro in the absence of a host plant.     

Functioning of glia and neurodegeneration in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The views on the role of glial tissue have changed greatly since the first studies in the field. The cells once regarded as “cell glue” have been shown to play important roles in development, trophic processes, production of navigation signals for axon growth, electric insulation of neurons, creation of a barrier between the brain and the hemolymph, control of extracellular homeostasis, and physiological functioning of the brain. Researchers all over the world are currently turning to Drosophila melanogaster, a well-characterized model organism in genetics, in order to investigate multiple molecular aspects of neurodegeneration processes, since the modeling of neurodegeneration mechanisms in Drosophila has a number of advantages. Fruit flies with a mutation in the swiss cheese (sws) gene show degeneration of neurons and surface glia cells of the optical lobe, and the protein product of the sws gene is essential for maintaining the functionality and integrity of the fly brain. The present review addresses the role of glial cells in Drosophila brain development and in the functioning of the adult fly brain as well as the pattern of expression of the gene sws and the distribution of the product of this gene in neurons and glia.     

Phenotypic effects of genetic variability in human clock genes on circadian and sleep parameters

Circadian rhythms and sleep are two separate but intimately related processes. Circadian rhythms are generated through the precisely controlled, cyclic expression of a number of genes designated clock genes. Genetic variability in these genes has been associated with a number of phenotypic differences in circadian as well as sleep parameters, both in mouse models and in humans. Diurnal preferences as determined by the selfreported Horne-Östberg (HÖ) questionnaire, has been associated with polymorphisms in the human genes CLOCK, PER1, PER2 and PER3. Circadian rhythm-related sleep disorders have also been associated with mutations and polymorphisms in clock genes, with the advanced type cosegrating in an autosomal dominant inheritance pattern with mutations in the genes PER2 and CSNK1D, and the delayed type associating without discernible Mendelian inheritance with polymorphisms in CLOCK and PER3. Several mouse models of clock gene null alleles have been demonstrated to have affected sleep homeostasis. Recent findings have shown that the variable number tandem polymorphism in PER3, previously linked to diurnal preference, has profound effects on sleep homeostasis and cognitive performance following sleep loss, confirming the close association between the processes of circadian rhythms and sleep at the genetic level.     

<Emphasis Type="Italic">Sip1</Emphasis> mutation suppresses the resistance of cerebral cortex neurons to hypoxia through the disturbance of mechanisms of hypoxic preconditioning

Mutation of Sip1 plays a key role in pathogenesis of the Mowat–Wilson syndrome characterized by the presence of pronounced epileptic signs in patients. As a rule, neurodegenerative processes are accompanied by hypoxic phenomena, glutamate toxicity, and death of nerve cells. The molecular mechanisms underlying these phenomena are multifaceted and complex. Hypoxia causes the leakage of glutamate and other neurotransmitters and thus activates glutamate receptors and channels of plasma membrane. Hypoxia is accompanied by increased synthesis and secretion of proteins-regulators of oxidative stress, inflammation, apoptosis, and synaptic transmission. In this work, we investigated the effect of Sip1 mutations on the neuronal sensitivity of the brain to hypoxia and the formation of the hypoxic preconditioning phenomenon. The preconditioning effect was evaluated by the degree of suppressing activity of NMDA receptors by hypoxic episodes. Using fluorescent microscopy, we showed that cortical neurons from the brain of heterozygous (Sip1 ^wt/fI) and homozygous (Sip1 ^fI/fI) mice are characterized by the absence of the hypoxic preconditioning effect, whereas in Sip1 ^wt/wt neurons the amplitudes of Ca²⁺ responses to the application of NMDA are suppressed after transient episodes of hypoxia. In addition, hypoxia exerted a significant toxic effect on Sip1fI/fI neurons, which was manifested not only by an increased sensitivity to a decrease of the oxygen partial pressure (pO₂) and increased amplitudes of Ca2+ responses to application of NMDA after each hypoxic episode, but also by death of a considerable number of cells.     

Genes <Emphasis Type="Italic">WHEAT FRIZZY PANICLE</Emphasis> and <Emphasis Type="Italic">SHAM RAMIFICATION 2</Emphasis> independently regulate differentiation of floral meristems in wheat

Background

Inflorescences of wheat species, spikes, are characteristically unbranched and bear one sessile spikelet at a spike rachis node. Development of supernumerary spikelets (SSs) at rachis nodes or on the extended rachillas is abnormal. Various wheat morphotypes with altered spike morphology, associated with the development of SSs, present an important genetic resource for studies on genetic regulation of wheat inflorescence development.

Results

Here we characterized diploid and tetraploid wheat lines of various non-standard spike morphotypes, which allowed for identification of a new mutant allele of the WHEAT FRIZZY PANICLE (WFZP) gene that determines spike branching in diploid wheat Ttiticum monococcum L. Moreover, we found that the development of SSs and spike branching in wheat T. durum Desf. was a result of a wfzp-A/TtBH-A1 mutation that originated from spontaneous hybridization with T. turgidum convar. сompositum (L.f.) Filat. Detailed characterization of the false-true ramification phenotype controlled by the recessive sham ramification 2 (shr2) gene in tetraploid wheat T. turgidum L. allowed us to suggest putative functions of the SHR2 gene that may be involved in the regulation of spikelet meristem fate and in specification of floret meristems. The results of a gene interaction test suggested that genes WFZP and SHR2 function independently in different processes during spikelet development, whereas another spike ramification gene(s) interact(s) with SHR2 and share(s) common functions.

Conclusions

SS mutants represent an important genetic tool for research on the development of the wheat spikelet and for identification of genes that control meristem activities. Further studies on different non-standard SS morphotypes and wheat lines with altered spike morphology will allow researchers to identify new genes that control meristem identity and determinacy, to elucidate the interaction between the genes, and to understand how these genes, acting in concert, regulate the development of the wheat spike.

     

A novel allele of <Emphasis Type="Italic">TaGW2</Emphasis>-<Emphasis Type="Italic">A1</Emphasis> is located in a finely mapped QTL that increases grain weight but decreases grain number in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Key message

A novel TaGW2-A1 allele was identified from a stable, robust QTL region, which is pleiotropic for thousand grain weight, grain number per spike, and grain morphometric parameters in wheat.

Abstract

Thousand grain weight (TGW) and grain number per spike (GNS) are two crucial determinants of wheat spike yield, and genetic dissection of their relationships can help to fine-tune these two components and maximize grain yield. By evaluating 191 recombinant inbred lines in 11 field trials, we identified five genomic regions on chromosomes 1B, 3A, 3B, 5B, or 7A that solely influenced either TGW or GNS, and a further region on chromosome 6A that concurrently affected TGW and GNS. The QTL of interest on chromosome 6A, which was flanked by wsnp_BE490604A_Ta_2_1 and wsnp_RFL_Contig1340_448996 and designated as QTgw/Gns.cau-6A, was finely mapped to a genetic interval shorter than 0.538 cM using near isogenic lines (NILs). The elite NILs of QTgw/Gns.cau-6A increased TGW by 8.33%, but decreased GNS by 3.05% in six field trials. Grain Weight 2 (TaGW2-A1), a well-characterized gene that negatively regulates TGW and grain width in wheat, was located within the finely mapped interval of QTgw/Gns.cau-6A. A novel and rare TaGW2-A1 allele with a 114-bp deletion in the 5′ flanking region was identified in the parent with higher TGW, and it reduced TaGW2-A1 promoter activity and expression. In conclusion, these results expand our knowledge of the genetic and molecular basis of TGW-GNS trade-offs in wheat. The QTLs and the novel TaGW2-A1 allele are likely useful for the development of cultivars with higher TGW and/or higher GNS.

     

Polymorphisms in ten candidate genes are associated with conformational and locomotive traits in Spanish Purebred horses

The Spanish Purebred horses, also known as Andalusian horses, compete to the highest standards in international dressage events. Gait and conformation could be used as early selection criteria to detect young horses with promising dressage ability. Although the genetic background of equine size variation has been recently uncovered, the genetic basis of horse conformational and locomotive traits is not known, hampered by the complex genetic architecture underlying quantitative traits and the lack of phenotypic data. The aim of this study was to validate the loci associated with size in 144 Spanish Purebred horses, and to seek novel associations between loci previously associated with the development of osteochondrosis (OC) lesions and 20 conformational and locomotive traits. Ten loci were associated with different conformational and locomotive traits (LCORL/NCAPG, HMGA2, USP31, MECR, COL24A1, MGP, FAM184B, PTH1R, KLF3 and SGK1), and the LCORL/NCAPG association with size in the Spanish Purebred horse was validated. Except for HMGA2, all polymorphisms seem to influence both the prevalence of OC lesions and morphological characters, supporting the link between conformation and OC. Also, the implication of most genes in either immune and inflammatory responses and cellular growth, or ossification processes, reinforces the role that these mechanisms have in the aetiology of OC, as well as their reflection on the general conformation of the individual. These polymorphisms could be used in marker-assisted selection (MAS) programmes to improve desirable conformational traits, but taking into account their possible detrimental effect on OC prevalence.     

Genetic structure of cultivated <Emphasis Type="Italic">Zanthoxylum</Emphasis> species investigated with SSR markers

Zanthoxylum is an economically and ecologically important genus of the Rutaceae family, of which Z. bungeanum and Z. armatum have a long history of cultivation in China. However, how the natural processes such as selection and drift and agriculture practices have influenced the genetic variation of cultivated Zanthoxylum species during long-term domestication remains elusive. Herein, we determined the population genetic structure of current widely cultivated Zanthoxylum species, Z. bungeanum and Z. armatum. Microsatellite markers revealed a high level of genetic variation and significant genetic differentiation for both species despite Z. bungeanum showed higher genetic diversity than Z. armatum. AMOVA indicated that most of the genetic variation exists within individuals rather than among provenances for both species. Population structure analyses generated three distinct groups within the entire accessions. All Z. bungeanum accessions were distinguished into two major geographic groups, north and south groups, with Qinling Mountains as the main geographic barrier to gene flow while a significant genetic differentiation was observed between cultivated and wild Z. armatum accessions. Mantel test of Z. bungeanum displayed a significant correlation between genetic and geographic distances within each inferred group but no correlation between genetic and geographic distance was observed when comparing genetic and geographic distances focusing only on pairwise of north vs. south provenances, ruling out the hypothesis that gene flow between north and south provenances followed an isolation-by-distance model. Our research provided a fundamental genetic profile that will improve the conservation and responsible exploitation of the extant germplasm of Zanthoxylum.     

Genetic drift and uniform selection shape evolution of most traits in <Emphasis Type="Italic">Eugenia dysenterica</Emphasis> DC. (Myrtaceae)

Knowing how microevolutionary processes, such as genetic drift and natural selection, shape variation in adaptive traits is strategic for conservation measures. One way to estimate local adaptation is to compare divergences in quantitative traits (Q_ST) and neutral loci (F_ST). Therefore, we have assessed the pattern of phenotypic and molecular genetic divergence among natural subpopulations of the fruit tree Eugenia dysenterica DC. A provenance and progeny test was performed to assess the quantitative traits of the subpopulations collected in a wide distribution area of the species in the Brazilian Cerrado. The sampled environments are in a biodiversity hotspot with heterogeneous soil and climate conditions. By associating quantitative trait variation in initial seedling development with neutral microsatellite marker variation, we tested the local adaptation of the traits by the Q_ST–F_ST contrast. Genetic drift was prevalent in the phenotypic differentiation among the subpopulations, although the traits seedling emergence time and root green mass, which are relevant for adaptation to the Cerrado climate, showed signs of uniform selection. Our results suggest that E. dysenterica has a spatial genetic structure divided into two large groups, separated by a line that divides the Cerrado biome in a southwestern to northeastern direction. This structure must be taken into account for managing E. dysenterica genetic resources both for conservation and breeding purposes.     

Neutral and non-neutral factors shape an emergent plant–antagonist interaction

Discerning the mechanisms responsible for emergent evolutionary radiations, community assembly, and the maintenance of diversity is necessary for understanding the evolutionary ecology of species interactions in changing landscapes. These processes can be driven by stochastic (neutral) factors, such as genetic drift, or deterministic (non-neutral) factors, such as the external environment and heritable phenotypic variation. Neutral and non-neutral factors can shape species interactions, but the relative influence of these different processes on antagonistic relationships is not well understood. We leveraged the recent discovery of a novel herbivore (Caloptilia triadicae) on invasive Chinese tallow (Triadica sebifera) to investigate the nature and relative importance of different factors influencing plant–antagonist interactions. We assessed measures of host attributes, herbivore demography and herbivory across the North American range of Triadica according to geography, environmental variation, and host genetic variation. We found that leaf toughness corresponded to genetic variation in Triadica, longitude, and mean temperature. Genetic variation in Triadica was the strongest predictor of herbivore abundance, especially for the early leaf mining stages, though herbivore abundance also corresponded to longitude. Model variables did not explain leaf damage, which was driven by interactions with late-stage larvae. Trends in herbivore demography were not consistent with previously reported geographic patterns of Triadica genetic variation related to tannin defense, but were consistent with patterns revealed by other studies of Triadica phenolic compounds and C:N, as well as low sensitivity of endophagous herbivores to tannins in the absence of parasitoids. Our findings suggest that even simple geographic mosaics of genetic and environmental variation, as well as distance-dependent dispersal, can influence the establishment and trajectory of novel species interactions.     

Genetic associations between ADHD and dopaminergic genes (<Emphasis Type="Italic">DAT1</Emphasis> and <Emphasis Type="Italic">DRD4</Emphasis>) VNTRs in Korean children

It is well known that dopaminergic genes affect the development of attention deficit hyperactivity disorder (ADHD) in various populations. Many studies have shown that variable number tandem repeats (VNTRs) located within the 3′-untranslated region of DAT1 and in exon 3 of DRD4 are associated with ADHD development; however, these results were inconsistent. Therefore, we investigated the genetic association between two VNTRs and ADHD in Korean children. We determined the VNTRs using PCR. We examined genotype and allele frequency differences between the experimental and control groups, along with the odds ratios, using Chi square and exact tests. We observed a significant association between the children with ADHD and the control group in the 10R/10R genotype of DAT1 VNTRs (p?=?0.025). In addition, the 11R allele of DAT1 VNTRs showed a higher frequency in the control group than in the ADHD group (p?=?0.023). Also, the short repeat (without 11R) and long repeat alleles (including 11R) were associated with ADHD (p?<?0.05). The analysis of DRD4 VNTRs revealed that the 2R allele is associated with ADHD (p?=?0.025). A significant result was also observed in long and short repeats (p?<?0.05). Additionally, ADHD subtypes showed that the DRD4 VNTRs are associated with combined and hyperactive-impulsive subtype groups (p?<?0.05). Therefore, our results suggest that DAT1 VNTRs and DRD4 VNTRs play a role in the genetic etiology of ADHD in Korean children.     

Genetic Association between Alzheimer’s Disease Risk Variant of the <Emphasis Type="Italic">PICALM</Emphasis> Gene and Auditory Event-Related Potentials in Aging

Aging and genetic predisposition are major risk factors in age-related neurodegenerative disorders. The most common neurodegenerative disorder is Alzheimer’s disease (AD). Genome-wide association studies (GWAS) have identified statistically significant association of the PICALM rs3851179 polymorphism with AD. The PICALM G allele increases the risk of AD, while the A allele has a protective effect. We examined the association of the PICALM rs3851179 polymorphism with parameters of the P3 component of auditory event-related potentials (ERPs) in 87 non-demented volunteers (age, 19–77 years) subdivided into two cohorts younger and older than 50 years of age. We found statistically significant association between the AD risk variant PICALM GG and increase in the P3 latency in subjects over 50 years old. The age-dependent increase in the P3 latency was more pronounced in the PICALM GG carriers than in the carriers of the PICALM AA and PICALM AG genotypes. The observed PICALM-associated changes in the neurophysiological processes indicate a decline in the information processing speed with aging due, probably, to neuronal dysfunction and subclinical neurodegeneration of the neuronal networks in the hippocampus and the frontal and parietal cortical areas. Such changes were less pronounced in the carriers of the PICALM gene A allele, which might explain the protective effect of this allele in the cognitive decline and AD development.     

A strong root-specific expression system for stable transgene expression in bread wheat

Key message

A strong, stable and root-specific expression system was developed from a rice root-specific GLYCINE - RICH PROTEIN 7 promoter for use as an enabling technology for genetic manipulation of wheat root traits.

Abstract

Root systems play an important role in wheat productivity. Genetic manipulation of wheat root traits often requires a root-specific or root-predominant expression system as an essential enabling technology. In this study, we investigated promoters from rice root-specific or root-predominant expressed genes for development of a root expression system in bread wheat. Transient expression analysis using a GREEN FLUORESCENT PROTEIN (GFP) reporter gene driven by rice promoters identified six promoters that were strongly expressed in wheat roots. Extensive organ specificity analysis of three rice promoters in transgenic wheat revealed that the promoter of rice GLYCINE-RICH PROTEIN 7 (OsGRP7) gene conferred a root-specific expression pattern in wheat. Strong GFP fluorescence in the seminal and branch roots of wheat expressing GFP reporter driven by the OsGRP7 promoter was detected in epidermal, cortical and endodermal cells in mature parts of the root. The GFP reporter driven by the promoter of rice METALLOTHIONEIN-LIKE PROTEIN 1 (OsMTL1) gene was mainly expressed in the roots with essentially no expression in the leaf, stem or seed. However, it was also expressed in floral organs including glume, lemma, palea and awn. In contrast, strong expression of rice RCg2 promoter-driven GFP was found in many tissues. The GFP expression driven by these three rice promoters was stable in transgenic wheat plants through three generations (T1–T3) examined. These data suggest that the OsGRP7 promoter can provide a strong, stable and root-specific expression system for use as an enabling technology for genetic manipulation of wheat root traits.

     

The response of transgenic <Emphasis Type="Italic">Brassica</Emphasis> species to salt stress: a review

Salt stress is considered one of the main abiotic factors to limit crop growth and productivity by affecting morpho-physiological and biochemical processes. Genetically, a number of salt tolerant Brassica varieties have been developed and introduced, but breeding of such varieties is time consuming. Therefore, current focus is on transgenic technology, which plays an important role in the development of salt tolerant varieties. Various salt tolerant genes have been characterized and incorporated into Brassica. Therefore, such genetic transformation of Brassica species is a significant step for improvement of crops, as well as conferring salt stress resistance qualities to Brassica species. Complete genome sequencing has made the task of genetically transforming Brassica species easier, by identifying desired candidate genes. The present review discusses relevant information about the principles which should be employed to develop transgenic Brassica species, and also will recommend tools for improved tolerance to salinity.