Key wheat GRF genes constraining wheat tillering of mutant dmc

Tillering is a key agronomy trait for wheat (Triticum aestivum L.) production. Previously, we have reported a dwarf-monoculm wheat mutant (dmc) obtained from cultivar Guomai 301 (wild type, WT), and found growth regulating factors (GRFs) playing important roles in regulating wheat tillering. This study is to systematically investigate the roles of all the wheat GRFs (T. aestivum GRFs, TaGRFs) in regulating tillering, and screen out the key regulators. A total of 30 TaGRFs were identified and their physicochemical properties, gene structures, conserved domains, phylogenetic relationships and tissue expression profiles were analyzed. The expression levels of all the TaGRFs were significantly lower in dmc than those in WT at early tillering stage, and the abnormal expressions of TaGRF2-7(A, B, D), TaGRF5-7D, TaGRF10-6(A, B, D) and TaGRF11-2A were major causes constraining the tillering of dmc. The transcriptions of TaGRFs were significantly affected by exogenous indole acetic acid (IAA) and gibberellin acid (GA3) applications, which suggested that TaGRFs as well as IAA, GA signaling were involved in controlling wheat tillering. This study provided valuable clues for functional characterization of GRF genes in wheat.

Insight into the mechanisms of terminal HS-tolerance in wheat mutant with improved nutritional quality through de novo transcriptome sequencing

Terminal HS is one of the main bottle-neck in wheat yield and grain-quality. Here, we have developed wheat mutant (M3) for HS-tolerance [parent-MP3054- C-306/CB.SPRING BW/CPAN2072 (Parentage)]. To elucidate the mechanism of thermotolerance in mutant, we performed de novo transcriptomic sequencing of mutant (M3), parent (P3), and mutant exposed to HS (M3H). We sequenced 6.5, 7.5, and 7.0 million reads in P3, M3 and M3H and generated 3,05,537 genes and 5,88,788 transcripts with an N50 of 1,349 bp. We observed 6,120 upregulated and 4,428 downregulated transcripts (M3 vs P3), 11,354 upregulated and 12,408 downregulated genes (M3H vs P3) and 4817 upregulated and 9085 downregulated genes (M3H vs M3). Some of the highly upregulated genes observed were HSP20, SOD, ABC transporters, HSF, etc. and downregulated genes were starch synthase, sucrose synthase, etc. Gene Ontology analysis showed ‘ATP-binding’ to be most enriched category. Carbon metabolism pathway was observed most altered under HS. We identified 41940 SSRs, 1,10,772 SNPs and 2432 InDels. Potential markers were observed lying on HSP, SOD, STK, and starch synthase. Biochemical markers based characterization showed wheat mutant to be better in HS-tolerance and grain-quality, as compared to parent.

Transcriptome Analysis Reveals a Potential Role of Benzoxazinoid in Regulating Stem Elongation in the Wheat Mutant qd

The stems of cereal crops provide both mechanical support for lodging resistance and a nutrient supply for reproductive organs. Elongation, which is considered a critical phase for yield determination in winter wheat (Triticum aestivum L.), begins from the first node detectable to anthesis. Previously, we characterized a heavy ion beam triggered wheat mutant qd, which exhibited an altered stem elongation pattern without affecting mature plant height. In this study, we further analyzed mutant stem developmental characteristics by using transcriptome data. More than 40.87 Mb of clean reads including at least 36.61 Mb of unique mapped reads were obtained for each biological sample in this project. We utilized our transcriptome data to identify 124,971 genes. Among these genes, 4,340 differentially expressed genes (DEG) were identified between the qd and wild-type (WT) plants. Compared to their WT counterparts, qd plants expressed 2,462 DEGs with downregulated expression levels and 1878 DEGs with upregulated expression levels. Using DEXSeq, we identified 2,391 counting bins corresponding to 1,148 genes, and 289 of them were also found in the DEG analysis, demonstrating differences between qd and WT. The 5,199 differentially expressed genes between qd and WT were employed for GO and KEGG analyses. Biological processes, including protein-DNA complex subunit organization, protein-DNA complex assembly, nucleosome organization, nucleosome assembly, and chromatin assembly, were significantly enriched by GO analysis. However, only benzoxazinoid biosynthesis pathway-associated genes were enriched by KEGG analysis. Genes encoding the benzoxazinoid biosynthesis enzymes Bx1, Bx3, Bx4, Bx5, and Bx8_9 were confirmed to be differentially expressed between qd and WT. Our results suggest that benzoxazinoids could play critical roles in regulating the stem elongation phenotype of qd.

Evaluation of advanced wheat mutant lines for food and feed quality.

The main goals of this study were to evaluate the agronomic performance of wheat mutant lines; to detect the effect of genotype, location and different fertilizer levels on analysed traits; to assess seed and feed quality; and to select best performing mutant lines for dual-purpose growing. Ten wheat mutant lines were sown on two locations in Macedonia, for evaluation of their agronomic performance. At both locations, grain yield, straw mass, harvest index, nitrogen use efficiency, nitrogen and protein content in seed and straw, neutral detergent fibre and acid detergent fibre in the straw were determined. In order to classify the genotypes based on all analysed traits, two-way cluster analysis was applied. According to their overall performance, at both locations and with the three different fertilization treatments, the mutant lines were classified in two main groups. The first cluster consisted of mutants 5/1-8, 2/2-21, 4/2-56 and 2/1-51, characterized by very high values for seed yield, straw yield and harvest index, and high to moderate values for all other traits. Only 4/2-56 had very low values for N and protein content in the seed. One mutant line, 6/2-2, did not belong to any of the groups and differed from all other genotypes based on its very low seed and straw yield and very high values for nitrogen and protein content in the straw and neutral detergent fibre. All other mutants belonged to the second group, with low to moderate yield and moderate to high values for the other traits. Mutant lines with the highest seed and straw yield, as well as the best quality of seed and straw under different management systems, were identified and after additional evaluation will be submitted for official variety registration.