Mapping QTL conferring flag leaf senescence in durum wheat cultivars.

Flag leaf senescence is a critical factor affecting the yield and quality of wheat. The aim of this study was to identify QTLs associated with flag leaf senescence in an F10 recombinant inbred line population derived from durum wheats UC1113 and Kofa. Bulked segregant analysis using the wheat 660K SNP array identified 3225 SNPs between extreme-phenotype bulks, and the differential SNPs were mainly clustered on chromosomes 1A, 1B, 3B, 5A, 5B, and 7A. BSR-Seq indicated that the significant SNPs were mainly located in two intervals of 354.0-389.0 Mb and 8.0-15.0 Mb on 1B and 3B, respectively. Based on the distribution of significant SNPs on chromosomes 1B and 3B, a total of 109 insertion/deletion (InDel) markers were developed, and 8 of them were finally used to map QTL in UC1113/Kofa population for flag leaf senescence. Inclusive composite interval mapping identified two major QTL in marker intervals Mar2005-Mar2116 and Mar207-Mar289, explaining 14.2-15.4% and 31.4-68.6% of the phenotypic variances across environments, respectively. Using BSR-Seq, gene expression and sequence analysis, the TraesCS1B02G211600 and TraesCS3B02G023000 were identified as candidate senescence-associated genes. This study has potential to be used in cloning key genes for flag leaf senescence and provides available molecular markers for genotyping and marker-assisted selection breeding. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01410-3.

Functions of lysine 2-hydroxyisobutyrylation and future perspectives on plants.

Lysine 2-hydroxyisobutyrylation (Khib) is a novel protein post-translational modifications (PTMs) observed in both eukaryotes and prokaryotes. Recent studies suggested that this novel PTM has the potential to regulate different proteins in various pathways. Khib is regulated by lysine acyltransferases and deacylases. This novel PTM reveals interesting connections between modifications and protein physiological functions, including gene transcription, glycolysis and cell growth, enzymic activity, sperm motility, and aging. Here, we review the discovery and the current understanding of this PTM. Then, we outline the networks of complexity of interactions among PTMs in plants, and raise possible directions of this novel PTM for future investigations in plants.

A cell wall invertase modulates resistance to fusarium crown rot and sharp eyespot in common wheat.

Fusarium crown rot (FCR) and sharp eyespot (SE) are serious soil-borne diseases in wheat and its relatives that have been reported to cause wheat yield losses in many areas. In this study, the expression of a cell wall invertase gene, TaCWI-B1, was identified to be associated with FCR resistance through a combination of bulk segregant RNA sequencing and genome resequencing in a recombinant inbred line population. Two bi-parental populations were developed to further verify TaCWI-B1 association with FCR resistance. Overexpression lines and ethyl methanesulfonate (EMS) mutants revealed TaCWI-B1 positively regulating FCR resistance. Determination of cell wall thickness and components showed that the TaCWI-B1-overexpression lines exhibited considerably increased thickness and pectin and cellulose contents. Furthermore, we found that TaCWI-B1 directly interacted with an alpha-galactosidase (TaGAL). EMS mutants showed that TaGAL negatively modulated FCR resistance. The expression of TaGAL is negatively correlated with TaCWI-B1 levels, thus may reduce mannan degradation in the cell wall, consequently leading to thickening of the cell wall. Additionally, TaCWI-B1-overexpression lines and TaGAL mutants showed higher resistance to SE; however, TaCWI-B1 mutants were more susceptible to SE than controls. This study provides insights into a FCR and SE resistance gene to combat soil-borne diseases in common wheat.

Genetic and molecular basis of carotenoid metabolism in cereals.

Carotenoids are vital pigments for higher plants and play a crucial function in photosynthesis and photoprotection. Carotenoids are precursors of vitamin A synthesis and contribute to human nutrition and health. However, cereal grain endosperm contains a minor carotenoid measure and a scarce supply of provitamin A content. Therefore, improving the carotenoids in cereal grain is of major importance. Carotenoid content is governed by multiple candidate genes with their additive effects. Studies on genes related to carotenoid metabolism in cereals would increase the knowledge of potential metabolic steps of carotenoids and enhance the quality of crop plants. Recognizing the metabolism and carotenoid accumulation in various staple cereal crops over the last few decades has broadened our perspective on the interdisciplinary regulation of carotenogenesis. Meanwhile, the amelioration in metabolic engineering approaches has been exploited to step up the level of carotenoid and valuable industrial metabolites in many crops, but wheat is still considerable in this matter. In this study, we present a comprehensive overview of the consequences of biosynthetic and catabolic genes on carotenoid biosynthesis, current improvements in regulatory disciplines of carotenogenesis, and metabolic engineering of carotenoids. A panoptic and deeper understanding of the regulatory mechanisms of carotenoid metabolism and genetic manipulation (genome selection and gene editing) will be useful in improving the carotenoid content of cereals.

Identification of TaGL1-B1 gene controlling grain length through regulation of jasmonic acid in common wheat.

Grain length is one of the most important factors in determining wheat yield. Here, a stable QTL for grain length was mapped on chromosome 1B in a F10 recombinant inbred lines (RIL) population, and the gene TaGL1-B1 encoding carotenoid isomerase was identified in a secondary large population through multiple strategies. The genome-wide association study (GWAS) in 243 wheat accessions revealed that the marker for TaGL1-B1 was the most significant among all chromosomes. EMS mutants of TaGL1 possessed significantly reduced grain length, whereas TaGL1-B1-overexpressed lines possessed significantly increased grain length. Moreover, TaGL1-B1 strongly interacted with TaPAP6. TaPAP6-overexpressed lines had significantly increased grain length. Transcriptome analysis suggested that TaPAP6 was possibly involved in the accumulation of JA (jasmonic acid). Consistently, JA content was significantly increased in the TaGL1-B1 and TaPAP6 overexpression lines. Additionally, the role of TaGL1-B1 in regulating carotenoids was verified through QTL mapping, GWAS, EMS mutants and overexpression lines. Notably, overexpression of TaGL1-B1 significantly increased wheat yield in multiple locations. Taken together, overexpression of TaGL1-B1 enhanced grain length, probably through interaction with TaPAP6 to cause the accumulation of JA that improved carotenoid content and photosynthesis, thereby resulted in increased wheat yield. This study provided valuable genes controlling grain length to improve yield and a potential insight into the molecular mechanism of modulating JA-mediated grain size in wheat.

Transcriptome Analysis Reveals Potential Mechanism in Storage Protein Trafficking within Developing Grains of Common Wheat.

Gluten proteins are the major storage protein fraction in the mature wheat grain. They are restricted to the starchy endosperm, which defines the viscoelastic properties of wheat dough. The synthesis of these storage proteins is controlled by the endoplasmic reticulum (ER) and is directed into the vacuole via the Golgi apparatus. In the present study, transcriptome analysis was used to explore the potential mechanism within critical stages of grain development of wheat cultivar "Shaannong 33" and its sister line used as the control (CK). Samples were collected at 10 DPA (days after anthesis), 14 DPA, 20 DPA, and 30 DPA for transcriptomic analysis. The comparative transcriptome analysis identified that a total of 18,875 genes were differentially expressed genes (DEGs) between grains of four groups "T10 vs. CK10, T14 vs. CK14, T20 vs. CK20, and T30 vs. CK30", including 2824 up-regulated and 5423 down-regulated genes in T30 vs. CK30. Further, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment highlighted the maximum number of genes regulating protein processing in the endoplasmic reticulum (ER) during grain enlargement stages (10-20 DPA). In addition, KEGG database analysis reported 1362 and 788 DEGs involved in translation, ribosomal structure, biogenesis, flavonoid biosynthesis pathway and intracellular trafficking, secretion, and vesicular transport through protein processing within ER pathway (ko04141). Notably, consistent with the higher expression of intercellular storage protein trafficking genes at the initial 10 DPA, there was relatively low expression at later stages. Expression levels of nine randomly selected genes were verified by qRT-PCR, which were consistent with the transcriptome data. These data suggested that the initial stages of "cell division" played a significant role in protein quality control within the ER, thus maintaining the protein quality characteristics at grain maturity. Furthermore, our data suggested that the protein synthesis, folding, and trafficking pathways directed by a different number of genes during the grain enlargement stage contributed to the observed high-quality characteristics of gluten protein in Shaannong 33 (Triticum aestivum L.).

Reduced expression of lipoxygenase genes improves flour processing quality in soft wheat.

Lipoxygenases (Loxs) are dioxygenases that play an important role in plant growth and defense. Loxs affect flour processing quality in common wheat (Triticum aestivum). We conducted a genome-wide association study (GWAS) that identified 306 significant single-nucleotide polymorphisms (SNPs) related to Lox activity in Chinese wheat accessions. Among them, a novel lipoxygenase-encoding (Lpx) gene, TaLpx-B4, was detected on chromosome 3B in a biparental population. Analysis of mutant wheat lines induced using ethyl methanesulfonate confirmed the role of TaLpx-B4 in modulating Lox activity. A phylogenetic tree of various plant Lpx genes indicated the predominance of the 9-Lpx type in common wheat. Further analysis revealed conserved intron number, exon length, and motif number in the TaLpx gene family. GWAS, linkage mapping, and gene annotation collectively showed that 14 out of 29 annotated TaLpx genes played a critical role in regulating Lox activity in the Chinese wheat accessions. Transgenic wheat grains with knockdown of Lpx family genes by RNAi showed significantly lower Lox activity than the wild type. One TaLpx-RNAi line had significantly reduced starch content and dough stability, and thus possessed relatively superior biscuit quality in soft wheat. Further analysis of the transcriptome, lipid components, and other metabolites revealed that knockdown of TaLpx genes significantly increased biscuit quality via changes in unsaturated fatty acid content as well as in starch, sucrose, and galactose metabolism. Our results provide new insights into the role of the TaLpx gene family that will be beneficial in improving soft wheat flour quality.