ABSTRACT: Small heat shock protein 17.8 (HSP17.8) is produced abundantly in plant cells under heat and other stress conditions and may play an important role in plant tolerance to stress environments. However, HSP17.8 may be differentially expressed in different accessions of a crop species exposed to identical stress conditions. The ability of different genotypes to adapt to various stress conditions resides in their genetic diversity. Allelic variations are the most common forms of genetic variation in natural populations. In this study, single nucleotide polymorphisms (SNPs) of the HSP17.8 gene were investigated across 210 barley accessions collected from 30 countries using EcoTILLING technology. Eleven SNPs including 10 from the coding region of HSP17.8 were detected, which form nine distinguishable haplotypes in the barley collection. Among the 10 SNPs in the coding region, six are missense mutations and four are synonymous nucleotide changes. Five of the six missense changes are predicted to be deleterious to HSP17.8 function. The accessions from Middle East Asia showed the higher nucleotide diversity of HSP17.8 than those from other regions and wild barley (H. spontaneum) accessions exhibited greater diversity than the cultivated barley (H. vulgare) accessions. Four SNPs in HSP17.8 were found associated with at least one of the agronomic traits evaluated except for spike length, namely number of grains per spike, thousand kernel weight, plant height, flag leaf area and leaf color. The association between SNP and these agronomic traits may provide new insight for study of the gene's potential contribution to drought tolerance of barley.
PLoS ONE 01/2013; 8(2):e56816. · 4.09 Impact Factor
ABSTRACT: Drought is one of the major factors limiting barley yields in many developing countries worldwide. The identification of molecular
markers linked to genes controlling drought tolerance in barley is one way to improve breeding efficiency. In this study,
we analyzed the quantitative trait loci (QTL) controlling chlorophyll content and chlorophyll fluorescence in 194 recombinant
inbred lines (RILs) developed from the cross between the cultivar ‘Arta’ and Hordeum spontaneum 41-1. Five traits, chlorophyll content, and four chlorophyll fluorescence parameters, namely initial fluorescence (Fo), maximum fluorescence (Fm), variable fluorescence (Fv), and maximum quantum efficiency of PSII (Fv/Fm) which are related to the activity of the photosynthetic apparatus, were measured under well-watered and drought stress conditions
at post-flowering stage. QTL analysis identified a total of nine and five genomic regions, under well-watered and drought
stress conditions, respectively, that were significantly associated with the expression of the five target traits at post-flowering
stage. No common QTL was detected except one for chlorophyll content, which was identified in both growth conditions, demonstrating
that the genetic control of the expression of the traits related to photosynthesis differed under different water conditions.
A QTL for Fv/Fm, which is related to the drought tolerance of photosynthesis was identified on chromosome 2H at 116cM in the linkage map
under drought stress. This QTL alone explained more than 15% of phenotypic variance of maximum quantum yield of PSII, and
was also associated with the expression of four other traits. In addition, another QTL for Fv/Fm was also located on the same chromosome (2H) but at 135.7cM explaining around 9% of the phenotypic variance under drought
conditions. The result presented here suggest that two major loci, located on chromosome 2H, are involved in the development
of functional chloroplast at post-flowering stage for drought tolerance of photosynthesis in barley under drought stress.
If validated in other populations, chlorophyll fluorescence parameters could be used as selection criteria for drought tolerance.
Euphytica 04/2012; 163(2):203-214. · 1.55 Impact Factor
ABSTRACT: Light-harvesting chlorophyll a/b-binding protein (LHCP) is one of the most abundant chloroplast proteins in plants. Its main function is to collect and transfer light energy to photosynthetic reaction centers. However, the roles of different LHCPs in light-harvesting antenna systems remain obscure. Exploration of nucleotide variation in the genes encoding LHCP can facilitate a better understanding of the functions of LHCP. In this study, nucleotide variations in Lhcb1, a LHCP gene in barley, were investigated across 292 barley accessions collected from 35 different countries using EcoTILLING technology, a variation of the Targeting Induced Local Lesions In Genomes (TILLING). A total of 23 nucleotide variations were detected including three insert/deletions (indels) and 20 single nucleotide polymorphisms (SNPs). Among them, 17 SNPs were in the coding region with nine missense changes. Two SNPs with missense changes are predicted to be deleterious to protein function. Seventeen SNP formed 31 distinguishable haplotypes in the barley collection. The levels of nucleotide diversity in the Lhcb1 locus differed markedly with geographic origins and species of accessions. The accessions from Middle East Asia exhibited the highest nucleotide and haplotype diversity. H. spontaneum showed greater nucleotide diversity than H. vulgare. Five SNPs in Lhcb1 were significantly associated with at least one of the six agronomic traits evaluated, namely plant height, spike length, number of grains per spike, thousand grain weight, flag leaf area and leaf color, and these SNPs may be used as potential markers for improvement of these barley traits.
PLoS ONE 01/2012; 7(5):e37573. · 4.09 Impact Factor
ABSTRACT: Drought tolerance is a key trait for increasing and stabilizing barley productivity in dry areas worldwide. Identification of the genes responsible for drought tolerance in barley (Hordeum vulgare L.) will facilitate understanding of the molecular mechanisms of drought tolerance, and also facilitate the genetic improvement of barley through marker-assisted selection or gene transformation. To monitor the changes in gene expression at the transcriptional level in barley leaves during the reproductive stage under drought conditions, the 22K Affymetrix Barley 1 microarray was used to screen two drought-tolerant barley genotypes, Martin and Hordeum spontaneum 41-1 (HS41-1), and one drought-sensitive genotype Moroc9-75. Seventeen genes were expressed exclusively in the two drought-tolerant genotypes under drought stress, and their encoded proteins may play significant roles in enhancing drought tolerance through controlling stomatal closure via carbon metabolism (NADP malic enzyme, NADP-ME, and pyruvate dehydrogenase, PDH), synthesizing the osmoprotectant glycine-betaine (C-4 sterol methyl oxidase, CSMO), generating protectants against reactive-oxygen-species scavenging (aldehyde dehydrogenase,ALDH, ascorbate-dependent oxidoreductase, ADOR), and stabilizing membranes and proteins (heat-shock protein 17.8, HSP17.8, and dehydrin 3, DHN3). Moreover, 17 genes were abundantly expressed in Martin and HS41-1 compared with Moroc9-75 under both drought and control conditions. These genes were possibly constitutively expressed in drought-tolerant genotypes. Among them, seven known annotated genes might enhance drought tolerance through signalling [such as calcium-dependent protein kinase (CDPK) and membrane steroid binding protein (MSBP)], anti-senescence (G2 pea dark accumulated protein, GDA2), and detoxification (glutathione S-transferase, GST) pathways. In addition, 18 genes, including those encoding Delta(l)-pyrroline-5-carboxylate synthetase (P5CS), protein phosphatase 2C-like protein (PP2C), and several chaperones, were differentially expressed in all genotypes under drought; thus they were more likely to be general drought-responsive genes in barley. These results could provide new insights into further understanding of drought-tolerance mechanisms in barley.
Journal of Experimental Botany 07/2009; 60(12):3531-44. · 5.36 Impact Factor
ABSTRACT: Barley genotypes, in particular landraces and wild species, represent an important source of variation for adaptive traits
that may contribute to increase yield and yield stability under drought conditions, and that could be introgressed into improved
varieties. Traits that have been investigated include physiological/biochemical and developmental/ morphological traits. Yield
performance under drought is particularly a complex phenomenon, and plants exhibit a diverse range of genetically complex
mechanisms for drought resistance. Quantitative trait loci (QTL) studies with and without H. spontaneum have shown that developmental genes, notably those involved in flowering time and plant stature show pleiotropic effects
on abiotic stress tolerance and ultimately determine yield. Problems associated with the hybridization of H. spontaneum such as alleles with deleterious effects on field performance could be best addressed in the advanced backcross (AB-) QTL
analysis. It was interesting to see that in AB-QTL populations like in balanced populations major QTL overshadowed minor QTL-alleles.
Nevertheless, crosses with H. spontaneum, AB-QTL populations and association studies with H. spontaneum have also identified new alleles and genes that are related to abiotic stress tolerance. In order to identify genes that
are related to drought tolerance microarrays analysis to monitor gene expression profiles for plants exposed to limited water
environment is performed. Several studies with rapid dehydration treatment have shown that osmotic-stress-inducible genes
could explain the response to drought stress in plants. Another development is the identification and use of nucleotide polymorphisms
(SNP) in genes related to abiotic stress tolerance. An understanding of the combined function and expression of genes involved
in various abiotic stresses, could help identify candidate genes underlying QTL of interest.
12/2007: pages 51-79;
ABSTRACT: Fusarium head blight (FHB), primarily caused by Fusarium graminearum Schw., is a destructive disease of wheat (Triticum aestivum L.). Although several genes related to FHB resistance have been reported, global analysis of gene expression in response to FHB infection remains to be explored. The expression patterns of transcriptomes from wheat spikes of FHB-resistant cultivar Ning 7840 and susceptible cultivar Clark were monitored during a period of 72 h after inoculation (hai) with F. graminearum. Microarray analysis, coupled with suppression subtractive hybridization technique, identified 44 significantly differentially expressed genes between cv. Ning 7840 and cv. Clark. More differentially expressed genes were identified from susceptible libraries than from resistance libraries. The up-regulation of defense-related genes in Ning 7840 relative to cultivar Clark occurred during early fungal stress (3-12 hai). Three genes, with unknown function that were up-regulated in cv. Ning 7840 at most time points investigated, might play an important role in enhancing FHB resistance.
Functional and Integrative Genomics 02/2007; 7(1):69-77. · 2.84 Impact Factor
ABSTRACT: To understand the mechanisms of aluminum (Al) tolerance in wheat (Triticum aestivum L.), suppression subtractive hybridization (SSH) libraries were constructed from Al-stressed roots of two near-isogenic lines (NILs). A total of 1,065 putative genes from the SSH libraries was printed in a cDNA array. Relative expression levels of those genes were compared between two NILs at seven time points of Al stress from 15 min to 7 days. Fifty-seven genes were differentially expressed for at least one time point of Al treatment. Among them, 28 genes including genes for aluminum-activated malate transporter-1, ent-kaurenoic acid oxidase-1, beta-glucosidase, lectin, histidine kinase, and phospoenolpyruvate carboxylase showed more abundant transcripts in Chisholm-T and therefore may facilitate Al tolerance. In addition, a set of genes related to senescence and starvation of nitrogen, iron, and sulfur, such as copper chaperone homolog, nitrogen regulatory gene-2, yellow stripe-1, and methylthioribose kinase, was highly expressed in Chisholm-S under Al stress. The results suggest that Al tolerance may be co-regulated by multiple genes with diverse functions, and those genes abundantly expressed in Chisholm-T may play important roles in enhancing Al tolerance. The down-regulated genes in Chisholm-S may repress root growth and restrict uptake of essential nutrient elements, and lead to root senescence.
Molecular and General Genetics 02/2007; 277(1):1-12. · 2.63 Impact Factor