The effect of visible light on mutagenic activity of 1-methyl-1-nitrosourea and 1-methyl-3-nitro-1-nitrosoguanidine

Irradiation with visible light reduced the mutagenic activity of 1-methyl-1-nitrosourea (MNH) and 1-methyl-3-nitro-1-nitrosoguanidine (MNG) solutions during their application onArabidopsis thaliana seeds for 24 hours. The antimutagenic effect of light was stronger with MNG than with MNH and in solutions buffered to pH 5 than in aqueous solutions. The decrease of activity of both the mutagens corresponded with the rate and degree of their photolysis. In the paper are presented the curves for the dependence of the decomposition of both substances and the formation of nitrous acid on pH and temperature of the solutions, amount of seeds.     

Cryptochrome 1b from Sweet Sorghum Regulates Photoperiodic Flowering,Photomorphogenesis, and ABA Response in Transgenic <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Cryptochromes are blue/UV-A light receptors that mediate various aspects of plant growth and development. Here, we report the function and signal mechanism of cryptochrome 1b (SbCRY1b) from sweet sorghum [Sorghum bicolor (L.) Moench], a typical short-day cereal plant, to explore its potential for genetic improvement of sweet sorghum varieties. SbCRY1b mRNA enrichment showed almost 24-h diurnal rhythms in both short-day (SD) and long-day (LD) conditions. Overexpression of SbCRY1b rescued the late-flowering and the long hypocotyl phenotypes of cry1cry2 double mutant in the transgenic Arabidopsis. SbCRY1b mediated Arabidopsis FT mRNA expression in LD and HY5 protein accumulation in response to blue light. SbCRY1b protein was located in both the nucleus and cytoplasm and was degraded by 26S proteasomes in response to blue light. SbCRY1b interacted, respectively, with Arabidopsis suppressor of PHYA-1051 (AtSPA1), E3 ubiquitin ligase constitutive photomorphogenesis 1 (AtCOP1), and a putative COP1 from sweet sorghum (SbCOP1) instead of SbSPA1 in vitro in a blue light-dependent manner. The observations imply SbCRY1b functions as a major regulator of photoperiodic flowering and its function is more similar to that of Arabidopsis CRY2. Moreover, SbCRY1b-overexpressed transgenic Arabidopsis showed oversensitivity to abscisic acid (ABA) during seed germination and root development. The expression of abscisic acid-insensitive 4 (ABI4), ABI5, abscisic acid responsive element-binding 1 (ABF1), (sucrose non-fermenting 1)-related protein kinase (SnRK2.3), RD29A, and EM6 was upregulated in the transgenic Arabidopsis. The results demonstrated that SbCRY1b may integrate blue light and ABA signals to regulate plant development.     

Drought-inducible expression of <Emphasis Type="Italic">Hv</Emphasis>-miR827 enhances drought tolerance in transgenic barley

Drought is one of the major abiotic stresses reducing crop yield. Since the discovery of plant microRNAs (miRNAs), considerable progress has been made in clarifying their role in plant responses to abiotic stresses, including drought. miR827 was previously reported to confer drought tolerance in transgenic Arabidopsis. We examined barley (Hordeum vulgare L. ‘Golden Promise’) plants over-expressing miR827 for plant performance under drought. Transgenic plants constitutively expressing CaMV-35S::Ath-miR827 and drought-inducible Zm-Rab17::Hv-miR827 were phenotyped by non-destructive imaging for growth and whole plant water use efficiency (WUE_wp). We observed that the growth, WUE_wp, time to anthesis and grain weight of transgenic barley plants expressing CaMV-35S::Ath-miR827 were negatively affected in both well-watered and drought-treated growing conditions compared with the wild-type plants. In contrast, transgenic plants over-expressing Zm-Rab17::Hv-miR827 showed improved WUE_wp with no growth or reproductive timing change compared with the wild-type plants. The recovery of Zm-Rab17::Hv-miR827 over-expressing plants also improved following severe drought stress. Our results suggest that Hv-miR827 has the potential to improve the performance of barley under drought and that the choice of promoter to control the timing and specificity of miRNA expression is critical.     

Glutathione reductase gene expression depends on chloroplast signals in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Glutathione reductase (EC 1.6.4.2) is one of the main antioxidant enzymes of the plant cell. In Arabidopsis thaliana, glutathione reductase is encoded by two genes: the gr1 gene encodes the cytosolic-peroxisomal form, and the gr2 gene encodes the chloroplast-mitochondrial form. Little is known about the regulation of expression of plant glutathione reductase genes. In the present work, we have demonstrated that gr2 (but not gr1) gene expression in Arabidopsis leaves changes depending on changes in redox state of the photosynthetic electron transport chain. Expression of both the gr1 and gr2 genes was induced by reactive oxygen species. In heterotrophic suspension cell culture of Arabidopsis, expression of both studied genes did not depend on H₂O₂ level or on changes in the redox state of the mitochondrial electron transport chain. Our data indicate that chloroplasts are involved in the regulation of the glutathione reductase gene expression in Arabidopsis.     

BvPRR7 is a cold responsive gene with a clock function in beet

The life cycle of flowering plants is partially defined by environmental cues like day length and temperature. In the model plant Arabidopsis thaliana and temperate cereals, such as barley (Hordeum vulgare) and wheat (Triticum spp.), differences in life cycle control have been associated with a natural variation in FLOWERING LOCUS C (FLC) and VERNALIZATION 1-3 (VRN1-3). In sugar beet (Beta vulgaris L.), variation in vernalization requirement and life cycle is determined by a major gene at the B locus. This gene has recently been identified as a pseudo-response regulator (PRR) gene BOLTING TIME CONTROL 1 (BTC1). A second gene in beet with homology to BTC1 and ARABIDOPSIS PSEUDO RESPONSE REGULATOR 7 (APRR7) in Arabidopsis was identified and termed Beta vulgaris PSEUDO RESPONSE REGULATOR 7 (BvPRR7). We functionally characterized BvPRR7 by transgenic analysis in Arabidopsis and expression profiling during development in beet. We show that BvPRR7 was diurnally regulated and responded to cold. Constitutive expression of BvPRR7 distorted diurnal rhythms and caused late flowering in Arabidopsis suggesting a conserved function of BvPRR7 in clock regulation. Conceivably, the retention of a functional role of BvPRR7 in clock regulation may have facilitated the evolution of a distinct role as major floral regulator of the second PRR7 homolog in beet, BTC1.     

Evaluation of Barley lncRNAs Expression Analysis in Salinity Stress

Long noncoding RNAs (lncRNAs) act important roles in a wide range of biological processes. The regulatory roles of lncRNAs are still poorly understood. One of the major problems of limiting plant productivity is the salinity in the worldwide that barley (Hordeum vulgare L.) seems to be relatively well adapted to salinity environments. The aim of this study is the investigation of lncRNAs’ expression levels on four barley genotypes (Hasat, Beysehir 99, Konevi 98 and Tarm 92) to 150 mM salt stress application during 3 days germination. Grains were placed randomly in petri dishes containing filter paper soaked in (a) only H₂O (control), (b) 150 mM NaCl for 72 h. RNA extraction were carried out using TriPure® reagent from root and shoot samples obtained after 150 mM salt treatment. Expression levels of CNT0018772 and CNT0031477 were determined by qPCR. Expression analysis demonstrated salinity effected expression levels of CNT0018772 and CNT0031477 on roots and shoots during germination. The expression levels of CNT0018772 for 150 mM salt applied groups were down-regulated raged between (log2–0.52 and–35.65) compared controls on roots and shoot. The expression levels of CNT0031477 in 150 mM salt applied groups were also down-regulated ranged between (log₂–10.40 and 33.59) compared controls on roots and shoot except for Tarm 92 variety. On the contrary, expression levels of CNT0031477 were up-regulated on root and shoot of Tarm 92. Comparison of CNT0018772 and CNT0031477 expression levels on roots, there was no significant difference between barley varieties compared to controls (p > 0.05). However, it was found there was statistically significant difference between 150 mM salt treatment and control groups for CNT0031477 expression levels (p < 0.05). It was determined Konevi 98 shoot control expression level was statistically higher than Tarm 92 shoot control. This is the first report about the lncRNAs expression levels of barley under salinity.     

Natural polymorphism of the plasmid double-stranded RNA of the <Emphasis Type="Italic">Saccharomyces</Emphasis> yeasts

The distribution and peculiarities of viral double-stranded RNA in natural Saccharomyces strains were studied. It is for the first time that the presence of the L and M fractions in the species S. kudriavzevii and S. mikatae has been documented. S. kudriavzevii has two types of M-dsRNA: M₁ and M₄, whereas the yeast S. mikatae is characterized by three types of plasmids: M₂–M₄. Plasmid dsRNAs are absent in S. cariocanus strains. A total of eleven types of M-dsRNA were identified; some of them were specific to particular species. Plasmids M₅–M₇ were revealed only in S. paradoxus strains and the yeast S. bayanus is characterized by M₈–M₁₁ double-stranded RNA. According to the results of phenotypic analysis, all the M-dsRNAs revealed were cryptic.     

Ectopic expression of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) <Emphasis Type="Italic">CsTIR</Emphasis>/<Emphasis Type="Italic">AFB</Emphasis> genes enhance salt tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Auxin receptors TIR1/AFBs play an essential role in a series of signaling network cascades. These F-box proteins have also been identified to participate in different stress responses via the auxin signaling pathway in Arabidopsis. Cucumber (Cucumis sativus L.) is one of the most important crops worldwide, which is also a model plant for research. In the study herein, two cucumber homologous auxin receptor F-box genes CsTIR and CsAFB were cloned and studied for the first time. The deduced amino acid sequences showed a 78% identity between CsTIR and AtTIR1 and 76% between CsAFB and AtAFB2. All these proteins share similar characteristics of an F-box domain near the N-terminus, and several Leucine-rich repeat regions in the middle. Arabidopsis plants ectopically overexpressing CsTIR or CsAFB were obtained and verified. Shorter primary roots and more lateral roots were found in these transgenic lines with auxin signaling amplified. Results showed that expression of CsTIR/AFB genes in Arabidopsis could lead to higher seeds germination rates and plant survival rates than wild-type under salt stress. The enhanced salt tolerance in transgenic plants is probably caused by maintaining root growth and controlling water loss in seedlings, and by stabilizing life-sustaining substances as well as accumulating endogenous osmoregulation substances. We proposed that CsTIR/AFB-involved auxin signal regulation might trigger auxin mediated stress adaptation response and enhance the plant salt stress resistance by osmoregulation.     

The gene conferring susceptibility to spot blotch caused by <Emphasis Type="Italic">Cochliobolus sativus</Emphasis> is located at the <Emphasis Type="Italic">Mla</Emphasis> locus in barley cultivar Bowman

Key message

We identified, fine mapped, and physically anchored a dominant spot blotch susceptibility gene Scs6 to a 125 kb genomic region containing the Mla locus on barley chromosome 1H.

Abstract

Spot blotch caused by Cochliobolus sativus is an important disease of barley, but the molecular mechanisms underlying resistance and susceptibility to the disease are not well understood. In this study, we identified and mapped a gene conferring susceptibility to spot blotch caused by the pathotype 2 isolate (ND90Pr) of C. sativus in barley cultivar Bowman. Genetic analysis of F₁ and F₂ progeny as well as F₃ families from a cross between Bowman and ND 5883 indicated that a single dominant gene (designated as Scs6) conferred spot blotch susceptibility in Bowman. Using a doubled haploid (DH) population derived from a cross between Calicuchima-sib (resistant) and Bowman-BC (susceptible), we confirmed that Scs6, contributed by Bowman-BC, was localized at the same locus as the previously identified spot blotch resistance allele Rcs6, which was contributed by Calicuchima-sib and mapped on the short arm of chromosome 1H. Using a genome-wide putative linear gene index of barley (Genome Zipper), 13 cleaved amplified polymorphism markers were developed from 11 flcDNA and two EST sequences and mapped to the Scs6/Rcs6 region on a linkage map constructed with the DH population. Further fine mapping with markers developed from barley genome sequences and F₂ recombinants derived from Bowman?×?ND 5883 and Bowman?×?ND B112 crosses delimited Scs6 in a 125 kb genomic interval harboring the Mla locus on the reference genome of barley cv. Morex. This study provides a foundational step for further cloning of Scs6 using a map-based approach.

     

Overexpression of <Emphasis Type="Italic">MeDREB1D</Emphasis> confers tolerance to both drought and cold stresses in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Cassava (Manihot esculenta) is an important tropical crop with extraordinary tolerance to drought stress but few reports on it. In this study, MeDREB1D was significantly and positively induced by drought stress. Two allelic variants of the gene named MeDREB1D(R-2) and MeDREB1D(Y-3) were identified. Overexpressing MeDREB1D(R-2) and MeDREB1D(Y-3) in Arabidopsis resulted in stronger tolerance to drought and cold stresses. Under drought stress, transgenic plants had more biomass, higher survival rates and less MDA content than wild-type plants. Under cold stress, transgenic plants also had higher survival rates than wild-type plants. To further characterize the molecular function of MeDREB1D, we conducted an RNA-Seq analysis of transgenic and wild-type Arabidopsis plants. The results showed that the Arabidopsis plants overexpressing MeDREB1D led to changes in downstream genes. Several POD genes, which may play a vital role in drought and cold tolerance, were up-regulated in transgenic plants. In brief, these results suggest that MeDREB1D can simultaneously improve plant tolerance to drought and cold stresses.