Seasonal variation in expression pattern of genes under HSP70

Heat shock protein 70 (HSP70) is one of the most abundant and best characterized heat shock protein family that consists of highly conserved stress proteins, expressed in response to stress, and plays crucial roles in environmental stress tolerance and adaptation. The present study was conducted to identify major types of genes under the HSP70 family and to quantify their expression pattern in heat- and cold-adapted Indian goats (Capra hircus) with respect to different seasons. Five HSP70 gene homologues to HSPA8, HSPA6, HSPA1A, HSPA1L, and HSPA2 were identified by gene-specific primers. The cDNA sequences showed high similarity to other mammals, and proteins have an estimated molecular weight of around 70 kDa. The expression of HSP70 genes was observed during summer and winter. During summer, the higher expression of HSPA8, HSPA6, and HSPA1A was observed, whereas the expression levels of HSPA1L and HSPA2 were found to be lower. It was also observed that the expression of HSPA1A and HSPA8 was higher during winter in both heat- and cold-adapted goats but downregulates in case of other HSPs. Therefore, both heat and cold stress induced the overexpression of HSP70 genes. An interesting finding that emerged from the study is the higher expression of HSP70 genes in cold-adapted goats during summer and in heat-adapted goats during winter. Altogether, the results indicate that the expression pattern of HSP70 genes is species- and breed-specific, most likely due to variations in thermal tolerance and adaptation to different climatic conditions.     

Genome-wide analysis of immunophilin FKBP genes and expression patterns in Zea mays

The receptors for the immunosuppression drugs FK506 and rapamycin are called FKBPs (FK506-binding proteins). FKBPs comprise a large family; they are found in many species, including bacteria, fungi, animals, and plants. As a class of peptidyl-prolyl cis-trans isomerase enzymes, the FKBP genes have been the focus of recent studies on plant stress tolerance and immunology. We identified and analyzed gene families encoding these proteins in maize using computational and molecular biology approaches. Thirty genes were found to encode putative FKBPs according to their FK506-binding domain. The FKBP genes can be classified into single domain and multiple domain members based on the number of the domains. By analysis of the physical locations, the 30 FKBP genes were found to be widely distributed on 10 chromosomes. After analysis of the FKBP phylogenetic tree in the maize genome, we found that the 30 genes revealed two major clades. Gene duplication played a major role in the evolution of FKBP genes, which suggests that the FKBP genes in maize have a pattern significantly different from that of these genes in rice. Based on semi-quantitative RT-PCR, we found that the 30 FKBPs were expressed differently in various tissues in maize, which suggests that FKBP genes play different roles in each tissue. Several FKBPs were expressed at higher levels in roots, indicating that these genes in maize may have similar or overlapping functions.     

Direct pollination of Zea mays ovules in vitro with Z. mays,Z. mexicana and Sorghum bicolor pollen

Summary Sorghum (Sorghum bicolor) pollen tubes penetrated and grew in corn (Zea mays) styles. The limited length of the sorghum pollen tubes (3–5 mm) and the absence of stigmatic hairs on the basal (5–10 mm) section of the corn styles prevented effective pollination in vivo and in vitro. Normal fertilisation occurred after in vitro pollination of exposed corn ovules with either corn or teosinte (Zea mexicana) pollen. Six per cent of corn ovules pollinated directly with sorghum pollen responded by rapid, massive growth of nucellar tissue.     

Transposon mutagenesis of nuclear photosynthetic genes in Zea mays

The discovery of a new maize (Zea mays L.) transposon system, Mutator, and the cloning of the 1.4 kilobase transposon, Mul, have made feasible the isolation of nuclear photosynthetic genes which are recognized only by their mutant phenotype. Mutant maize plants which express a high chlorophyll fluorescent (hcf) phenotype due to a defect in the electron transport or photophosphorylation apparatus have been isolated following mutagenesis with an active Mutator stock. The affected genes and their products in these mutants are inaccessible to classical methods of analysis. However, mutagenesis with the Mutator transposon makes it possible to isolate these genes.Although the PSII-deficient mutant hcf3 has been thoroughly studied by classical photo-biological methods, the nature of the lesion which results in the observed phenotype has not been established. A Mutator-induced allele of hcf3 has been isolated. A fragment of genomic DNA has been identified which is homologous to Mul and co-segregates with the mutant phenotype. This fragment is expected to contain a portion of the hcf3 locus which will be used to clone the normal gene. Direct study of the gene can provide insight into the nature and function of its polypeptide product.This approach can be used to study any photosynthetic gene which has been interrupted by a transposon. The isolation of more than 100 different chemically-induced hcf mutants, most of which can not be fully characterized using classical means, indicates the wealth of information which can be obtained using a transposon tagging technique.     

Major regulatory genes in maize contribute to standing variation in teosinte (Zea mays ssp. parviglumis)

In plants, many major regulatory genes that control plant growth and development have been identified and characterized. Despite a detailed knowledge of the function of these genes little is known about how they contribute to the natural variation for complex traits. To determine whether major regulatory genes of maize contribute to standing variation in Balsas teosinte we conducted association mapping in 584 Balsas teosinte individuals. We tested 48 markers from nine candidate regulatory genes against 13 traits for plant and inflorescence architecture. We identified significant associations using a mixed linear model that controls for multiple levels of relatedness. Ten associations involving five candidate genes were significant after correction for multiple testing, and two survive the conservative Bonferroni correction. zfl2, the maize homolog of FLORICAULA of Antirrhinum, was associated with plant height. zap1, the maize homolog of APETALA1 of Arabidopsis, was associated with inflorescence branching. Five SNPs in the maize domestication gene, teosinte branched1, were significantly associated with either plant or inflorescence architecture. Our data suggest that major regulatory genes in maize do play a role in the natural variation for complex traits in teosinte and that some of the minor variants we identified may have been targets of selection during domestication.     

Isolation and characterization of three polyamine oxidase genes from Zea mays

Isolation and sequencing of three genes, MPAO1, MPAO2 and MPAO3, coding for polyamine oxidase (PAO) from maize (Zea mays) are reported here. Gene organization is extremely conserved among these copies, being composed of eight exons and seven introns. Furthermore, these genes encode for a protein of an almost identical amino acid sequence. These data suggest that the three MPAO copies have been derived from gene duplication of a common ancestor gene. Long inverted repeat sequences, also present in other maize genes, have been found within the second intron. Promoter sequences of MPAO1 and MPAO2 genes have been analysed for putative cis-acting elements. According to genomic Southern blot analysis, the MPAO gene family in maize and other monocots is represented by a small number of copies. Northern and western blot analysis have revealed a tissue-specific accumulation of both MPAO mRNA and protein.     

Alfalfa plant-derived biostimulant stimulate short-term growth of salt stressed Zea mays L. plants

Background & Aims

The effects of an alfalfa plant (Medicago sativa L.) hydrolysate-based biostimulant (EM) containing triacontanol (TRIA) and indole-3-acetic acid (IAA) were tested in salt-stressed maize plants.

Methods

Plants were grown for 2 weeks in the absence of NaCl or in the presence (25, 75 and 150 mM). On the 12th day, plants were supplied for 48 h with 1.0 mg L^?1 EM or 11.2 μM TRIA.

Results

EM and TRIA stimulated the growth and nitrogen assimilation of control plants to a similar degree, while NaCl reduced plant growth, SPAD index and protein content. EM or TRIA increased plant biomass under salinity conditions. Furthermore, EM induced the activity of enzymes functioning in nitrogen metabolism. The activity of antioxidant enzymes and the synthesis of phenolics were induced by salinity, but decreased after EM treatment. The enhancement of phenylalanine ammonia-lyase (PAL) activity and gene expression by EM was consistent with the increase of flavonoids.

Conclusion

The present study proves that the EM increases plant biomass even when plants are grown under salinity conditions. This was likely because EM stimulated plant nitrogen metabolism and antioxidant systems. Therefore, EM may be proposed as bioactive product in agriculture to help plants overcome stress situations.     

The role of genetic variation in Zea mays response to beneficial endophytes

Plant Growth Regulation - Growth-promoting endophytes have great potential to boost crop production and sustainability. There is, however, a lack of research on how differences in the plant host...     

Cytological study on water stress during germination of Zea mays

Summary Kernels of Zea mays were subjected to dehydration treatment at various times during germination. Embryos from kernels dehydrated during the first 36 h of germination are resistant to dehydration and subsequently germinate earlier than controls. Dehydration of kernels germinated during 72h leads to an irreversible arrest of growth of the embryos. However, autoradiographic observations showed that these embryos are still able to incorporate [³H] uridine and probably [4-5-³H] lysine. Incorporation of [³H] thymidine does not occur. The effect of dehydration on root ultrastructure was studied. In embryos dehydrated after 24 h and 72 h of germination, condensation of chromatin is seen and association of elements of rough endoplasmic reticulum with vacuoles and glyoxysomes can be noted. These changes are reversible in drought-resistant embryos and irreversible in drought-sensitive embryos. However, more notable changes than those seen after 24 h can be observed in embryos dehydrated after 72 h of germination: mitochondria and proplastids can not be distinguished with certainty, glyoxysomes fuse and preferably dispose at the periphery of the cell. Rehydration of drought-sensitive embryos causes breakdown in plasma and nuclear membranes, which leads to the loss of cellular compartimentalization. Moreover, the chromatin remains definitively condensed and has lost its function of genetic regulation.     

Comparison of maize (Zea mays L.) F1-hybrid and parental inbred line primary root transcriptomes suggests organ-specific patterns of nonadditive gene expression and conserved expression trends

The phenomenon of heterosis describes the increased agronomic performance of heterozygous F(1) plants compared to their homozygous parental inbred plants. Heterosis is manifested during the early stages of root development in maize. The goal of this study was to identify nonadditive gene expression in primary roots of maize hybrids compared to the average expression levels of their parental inbred lines. To achieve this goal a two-step strategy was used. First, a microarray preselection of nonadditively expressed candidate genes was performed. Subsequently, gene expression levels in a subset of genes were determined via high-throughput quantitative real-time (qRT)-PCR experiments. Initial microarray experiments identified 1941 distinct microarray features that displayed nonadditive gene expression in at least 1 of the 12 analyzed hybrids compared to the midparent value of their parental inbred lines. Most nonadditively expressed genes were expressed between the parental values (>89%). Comparison of these 1941 genes with nonadditively expressed genes identified in maize shoot apical meristems via the same experimental procedure in the same genotypes revealed significantly less overlap than expected by pure chance. This finding suggests organ-specific patterns of nonadditively expressed genes. qRT-PCR analyses of 64 of the 1941 genes in four different hybrids revealed conserved patterns of nonadditively expressed genes in different hybrids. Subsequently, 22 of the 64 genes that displayed nonadditive expression in all four hybrids were analyzed in 12 hybrids that were generated from four inbred lines. Among those genes a superoxide dismutase 2 was expressed significantly above the midparent value in all 12 hybrids and might thus play a protective role in heterosis-related antioxidative defense in the primary root of maize hybrids. The findings of this study are consistent with the hypothesis that both global expression trends and the consistent differential expression of specific genes contribute to the organ-specific manifestation of heterosis.     

Chromosomal location of the catalase structural genes in Zea mays using B-A translocations

Summary B-A translocations have been used to map the catalase genes, Cat1, Cat2, and Cat3 of Zea mays. Cat1 was found to be on the short arm of chromosome 5, 9.1 map units from brittle endosperm (bt ₁). Cat2 was located on chromosome 1S, while Cat3 was located on the distal half of chromosome 1L. There was no linkage between Cat2 and Cat3. The significance of mapping the catalase structural genes is discussed.This research was supported by Grant No. GM22733 from the National Institute of General Medical Sciences, National Institutes of Health, USPHS to JGS.This is Paper No. 6437 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC     

Genetic variation for the response to ploidy change in Zea mays L.

Polyploidization is an important process in the evolutionary history of most eukaryotic species. It oftentimes causes large-scale genomic reorganizations and is accompanied by a wide variety of phenotypic alterations in morphology, niche preference and fitness characteristics. Despite their importance, the morphological effects of alterations in ploidy are not well understood. We investigated these changes in four diverse maize inbred lines, using monoploid, diploid, triploid and tetraploid derivatives, measuring 13 characters in a randomized field study. Employing several analysis of variance approaches, we find that all characters investigated strongly respond to alterations in ploidy. This response appears to have two sources: one source is shared by all inbred lines and constitutes a common response to ploidy change. The other source is genotype specific and results in a response to ploidy change that varies among inbred lines. This finding demonstrates the existence of genetic variation for the morphological response to ploidy change in Zea mays.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.