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RWP-RKs represent a small family of transcription factors (TFs) that are unique to plants and function particularly under conditions of nitrogen starvation. These RWP-RKs have been classified in two sub-families, NLPs (NIN-like proteins) and RKDs (RWP-RK domain proteins). NLPs regulate tissue-specific expression of genes involved in nitrogen use efficiency (NUE) and RKDs regulate expression of genes involved in gametogenesis/embryogenesis. During the present study, using in silico approach, 37 wheat RWP-RK genes were identified, which included 18 TaNLPs (2865 to 7340 bp with 4/5 exons), distributed on 15 chromosomes from 5 homoeologous groups (with two genes each on 4B,4D and 5A) and 19 TaRKDs (1064 to 5768 bp with 1 to 6 exons) distributed on 12 chromosomes from 4 homoeologous groups (except groups 1, 4 and 5); 2–3 splice variants were also available in 9 of the 37 genes. Sixteen (16) of these genes also carried 24 SSRs (simple sequence repeats), while 11 genes had targets for 13 different miRNAs. At the protein level, MD simulation analysis suggested their interaction with nitrate-ions. Significant differences were observed in the expression of only two (TaNLP1 and TaNLP2) of the nine representative genes that were used for in silico expression analysis under varying levels of N at post-anthesis stage (data for other genes was not available for in silico expression analysis). Differences in expression were also observed during qRT-PCR, when expression of four representative genes (TaNLP2, TaNLP7, TaRKD6 and TaRKD9) was examined in roots and shoots of seedlings (under different conditions of N supply) in two contrasting genotypes which differed in NUE (C306 with low NUE and HUW468 with high NUE). These four genes for qRT-PCR were selected on the basis of previous literature, level of homology and the level of expression (in silico study). In particular, the TaNLP7 gene showed significant up-regulation in the roots and shoots of HUW468 (with higher NUE) during N-starvation; this gene has already been characterized in Arabidopsis and tobacco, and is known to be involved in nitrate-signal transduction pathway. [ABSTRACT FROM AUTHOR]

In bread wheat, QTL interval mapping was conducted for nine important drought responsive agronomic traits. For this purpose, a doubled haploid (DH) mapping population derived from Kukri/Excalibur was grown over three years at four separate locations in India, both under irrigated and rain-fed environments. Single locus analysis using composite interval mapping (CIM) allowed detection of 98 QTL, which included 66 QTL for nine individual agronomic traits and 32 QTL, which affected drought sensitivity index (DSI) for the same nine traits. Two-locus analysis allowed detection of 19 main effect QTL (M-QTL) for four traits (days to anthesis, days to maturity, grain filling duration and thousand grain weight) and 19 pairs of epistatic QTL (E-QTL) for two traits (days to anthesis and thousand grain weight). Eight QTL were common in single locus analysis and two locus analysis. These QTL (identified both in single- and two-locus analysis) were distributed on 20 different chromosomes (except 4D). Important genomic regions on chromosomes 5A and 7A were also identified (5A carried QTL for seven traits and 7A carried QTL for six traits). Marker-assisted recurrent selection (MARS) involving pyramiding of important QTL reported in the present study, together with important QTL reported earlier, may be used for improvement of drought tolerance in wheat. In future, more closely linked markers for the QTL reported here may be developed through fine mapping, and the candidate genes may be identified and used for developing a better understanding of the genetic basis of drought tolerance in wheat. [ABSTRACT FROM AUTHOR]

Genome wide association study (GWAS) was conducted for 14 agronomic traits in wheat following widely used single locus single trait (SLST) approach, and two recent approaches viz. multi locus mixed model (MLMM), and multi-trait mixed model (MTMM). Association panel consisted of 230 diverse Indian bread wheat cultivars (released during 1910–2006 for commercial cultivation in different agro-climatic regions in India). Three years phenotypic data for 14 traits and genotyping data for 250 SSR markers (distributed across all the 21 wheat chromosomes) was utilized for GWAS. Using SLST, as many as 213 MTAs (p ≤ 0.05, 129 SSRs) were identified for 14 traits, however, only 10 MTAs (~9%; 10 out of 123 MTAs) qualified FDR criteria; these MTAs did not show any linkage drag. Interestingly, these genomic regions were coincident with the genomic regions that were already known to harbor QTLs for same or related agronomic traits. Using MLMM and MTMM, many more QTLs and markers were identified; 22 MTAs (19 QTLs, 21 markers) using MLMM, and 58 MTAs (29 QTLs, 40 markers) using MTMM were identified. In addition, 63 epistatic QTLs were also identified for 13 of the 14 traits, flag leaf length (FLL) being the only exception. Clearly, the power of association mapping improved due to MLMM and MTMM analyses. The epistatic interactions detected during the present study also provided better insight into genetic architecture of the 14 traits that were examined during the present study. Following eight wheat genotypes carried desirable alleles of QTLs for one or more traits, WH542, NI345, NI170, Sharbati Sonora, A90, HW1085, HYB11, and DWR39 (Pragati). These genotypes and the markers associated with important QTLs for major traits can be used in wheat improvement programs either using marker-assisted recurrent selection (MARS) or pseudo-backcrossing method. [ABSTRACT FROM AUTHOR]

Wheat is an important staple crop, and its productivity is severely constrained by drought stress (DS). An understanding of the molecular basis of drought tolerance is necessary for genetic improvement of wheat for tolerance to DS. The two-component system (TCS) serves as a common sensor-regulator coupling mechanism implicated in the regulation of diverse biological processes (including response to DS) not only in prokaryotes, but also in higher plants. In the latter, TCS generally consists of two signalling elements, a histidine kinase (HK) and a response regulator (RR) associated with an intermediate element called histidine phosphotransferase (HPT). Keeping in view the possible utility of TCS in developing water use efficient (WUE) wheat cultivars, we identified and characterized 62 wheat genes encoding TCS elements in a silico study; these included 7 HKs, 45 RRs along with 10 HPTs. Twelve of the 62 genes showed relatively higher alterations in the expression under drought. The quantitative RT-PCR (qRT-PCR)-based expression analysis of these 12 TCS genes was carried out in wheat seedlings of a drought sensitive (HD2967) and a tolerant (Dharwar Dry) cultivar subjected to either dehydration stress or cytokinin treatment. The expression of these 12 genes under dehydration stress differed in sensitive and tolerant genotypes, even though for individual genes, both showed either up-regulation or down-regulation. In response to the treatment of cytokinin, the expression of type-A RR genes was higher in the tolerant genotype, relative to that in the sensitive genotype, the situation being reverse for the type-B RRs. These results have been discussed in the context of the role of TCS elements in drought tolerance in wheat. [ABSTRACT FROM AUTHOR]

It is known that nearly one-third of the world population currently suffers from malnutrition due to lack of availability of adequate quantity of protein, vitamins and a number of micronutrients including Fe and Zn in their diet. A lack of other desirable bioactive compounds and dietary fibres ( DF) in the diet also causes a variety of diseases. In some regions of the world, occurrence of Cd and As in wheat grain in excess of tolerance limits also adversely affects human health. In this short review, we summarize the current status of knowledge about the genetic control of the accumulation of a variety of nutritional constituents in wheat grain and then describe examples where noticeable improvements have been made using breeding approaches. We also describe the gaps that need to be bridged for better understanding of the genetic architecture of these important traits. The development and use of molecular markers in marker-assisted selection ( MAS) for developing wheat varieties with improved grain quality has also been discussed. [ABSTRACT FROM AUTHOR]

Epigenetic modifications act as conductors of inheritable alterations in gene expression, all while keeping the DNA sequence intact, thereby playing a pivotal role in shaping plant growth and development. This review article presents an overview of techniques employed to investigate and manipulate epigenetic diversity in crop plants, focusing on both naturally occurring and artificially induced epialleles. The significance of epigenetic modifications in facilitating adaptive responses is explored through the examination of how various biotic and abiotic stresses impact them. Further, environmental chemicals are explored for their role in inducing epigenetic changes, particularly focusing on inhibitors of DNA methylation like 5-AzaC and zebularine, as well as inhibitors of histone deacetylation including trichostatin A and sodium butyrate. The review delves into various approaches for generating epialleles, including tissue culture techniques, mutagenesis, and grafting, elucidating their potential to induce heritable epigenetic modifications in plants. In addition, the ground breaking CRISPR/Cas is emphasized for its accuracy in targeting specific epigenetic changes. This presents a potent tools for deciphering the intricacies of epigenetic mechanisms. Furthermore, the intricate relationship between epigenetic modifications and non-coding RNA expression, including siRNAs and miRNAs, is investigated. The emerging role of exo-RNAi in epigenetic regulation is also introduced, unveiling its promising potential for future applications. The article concludes by addressing the opportunities and challenges presented by these techniques, emphasizing their implications for crop improvement. Conclusively, this extensive review provides valuable insights into the intricate realm of epigenetic changes, illuminating their significance in phenotypic plasticity and their potential in advancing crop improvement. • Epigenetic changes impact plant growth without altering DNA. • Crop plant epigenetic diversity, including natural and induced variations. • Creation of epialleles: tissue culture, mutagenesis, grafting, and precise CRISPR/Cas targeting. • Opportunities and obstacles in epigenetic techniques for crop improvement. • Epigenetic research's promise for improving crop yields and resilience to changing environments. [ABSTRACT FROM AUTHOR]