GhJUB1_3-At positively regulate drought and salt stress tolerance under control of GhHB7, GhRAP2-3 and GhRAV1 in Cotton.

Climate change severely affects crop production. Cotton is one of the primary fiber crops in the world and its production is susceptible to various environmental stresses, especially drought and salinity. Development of stress tolerant genotypes is the only way to escape from these environmental constraints. We identified sixteen homologs of the Arabidopsis JUB1 gene in cotton. Expression of GhJUB1_3-At was significantly induced in the temporal expression analysis of GhJUB1 genes in the roots of drought tolerant (H177) and susceptible (S9612) cotton genotypes under drought. The silencing of the GhJUB1_3-At gene alone and together with its paralogue GhJUB1_3-Dt reduced the drought tolerance in cotton plants. The transgenic lines exhibited tolerance to the drought and salt stress as compared to the wildtype (WT). The chlorophyll and relative water contents of wildtype decreased under drought as compared to the transgenic lines. The transgenic lines showed decreased H2O2 and increased proline levels under drought and salt stress, as compared to the WT, indicating that the transgenic lines have drought and salt stress tolerance. The expression analysis of the transgenic lines and WT revealed that GAI was upregulated in the transgenic lines in normal conditions as compared to the WT. Under drought and salt treatment, RAB18 and RD29A were strongly upregulated in the transgenic lines as compared to the WT. Conclusively, GhJUB1_3-At is not an auto activator and it is regulated by the crosstalk of GhHB7, GhRAP2-3 and GhRAV1. GhRAV1, a negative regulator of abiotic stress tolerance and positive regulator of leaf senescence, suppresses the expression of GhJUB1_3-At under severe circumstances leading to plant death.

Transcriptome analysis reveals key regulatory genes for root growth related to potassium utilization efficiency in rapeseed (Brassica napus L.).

Root system architecture (RSA) is the primary predictor of nutrient intake and significantly influences potassium utilization efficiency (KUE). Uncertainty persists regarding the genetic factors governing root growth in rapeseed. The root transcriptome analysis reveals the genetic basis driving crop root growth. In this study, RNA-seq was used to profile the overall transcriptome in the root tissue of 20 Brassica napus accessions with high and low KUE. 71,437 genes in the roots displayed variable expression profiles between the two contrasting genotype groups. The 212 genes that had varied expression levels between the high and low KUE lines were found using a pairwise comparison approach. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional classification analysis revealed that the DEGs implicated in hormone and signaling pathways, as well as glucose, lipid, and amino acid metabolism, were all differently regulated in the rapeseed root system. Additionally, we discovered 33 transcription factors (TFs) that control root development were differentially expressed. By combining differential expression analysis, weighted gene co-expression network analysis (WGCNA), and recent genome-wide association study (GWAS) results, four candidate genes were identified as essential hub genes. These potential genes were located fewer than 100 kb from the peak SNPs of QTL clusters, and it was hypothesized that they regulated the formation of the root system. Three of the four hub genes' homologs-BnaC04G0560400ZS, BnaC04G0560400ZS, and BnaA03G0073500ZS-have been shown to control root development in earlier research. The information produced by our transcriptome profiling could be useful in revealing the molecular processes involved in the growth of rapeseed roots in response to KUE.

Silencing of GhORP_A02 enhances drought tolerance in Gossypium hirsutum.

BACKGROUND: ORP (Oxysterol-binding protein-related proteins) genes play a role in lipid metabolism, vesicular transferring and signaling, and non-vesicular sterol transport. However, no systematic identification and analysis of ORP genes have been reported in cotton. RESULT: In this study, we identified 14, 14, 7, and 7 ORP genes in G. hirsutum, G. barbadense, G. arboreum, and G. raimondii, respectively. Phylogenetic analysis showed that all ORP genes could be classified into four groups. Gene structure and conserved motif analysis suggest that the function of this gene family was conserved. The Ka/Ks analysis showed that this gene family was exposed to purifying selection during evolution. Transcriptome data showed that four ORP genes, especially GhORP_A02, were induced by abiotic stress treatment. The cis-acting elements in the ORP promoters were responsive to phytohormones and various abiotic stresses. The silenced plants of GhORP_A02 were more sensitive to drought stress when compared to control. CONCLUSION: The major finding of this study shed light on the potential role of ORP genes in abiotic stress and provided a fundamental resource for further analysis in cotton.

Genome-Wide Association Studies of Root-Related Traits in Brassica napus L. under Low-Potassium Conditions.

Roots are essential organs for a plant's ability to absorb water and obtain mineral nutrients, hence they are critical to its development. Plants use root architectural alterations to improve their chances of absorbing nutrients when their supply is low. Nine root traits of a Brassica napus association panel were explored in hydroponic-system studies under low potassium (K) stress to unravel the genetic basis of root growth in rapeseed. The quantitative trait loci (QTL) and candidate genes for root development were discovered using a multilocus genome-wide association study (ML-GWAS). For the nine traits, a total of 453 significant associated single-nucleotide polymorphism (SNP) loci were discovered, which were then integrated into 206 QTL clusters. There were 45 pleiotropic clusters, and qRTA04-4 and qRTC04-7 were linked to TRL, TSA, and TRV at the same time, contributing 5.25-11.48% of the phenotypic variance explained (PVE) to the root traits. Additionally, 1360 annotated genes were discovered by examining genomic regions within 100 kb upstream and downstream of lead SNPs within the 45 loci. Thirty-five genes were identified as possibly regulating root-system development. As per protein-protein interaction analyses, homologs of three genes (BnaC08g29120D, BnaA07g10150D, and BnaC04g45700D) have been shown to influence root growth in earlier investigations. The QTL clusters and candidate genes identified in this work will help us better understand the genetics of root growth traits and could be employed in marker-assisted breeding for rapeseed adaptable to various conditions with low K levels.

Genetic Dissection of Mature Root Characteristics by Genome-Wide Association Studies in Rapeseed (Brassica napus L.).

Roots are complicated quantitative characteristics that play an essential role in absorbing water and nutrients. To uncover the genetic variations for root-related traits in rapeseed, twelve mature root traits of a Brassica napus association panel were investigated in the field within three environments. All traits showed significant phenotypic variation among genotypes, with heritabilities ranging from 55.18% to 79.68%. Genome-wide association studies (GWAS) using 20,131 SNPs discovered 172 marker-trait associations, including 103 significant SNPs (-log10 (p) > 4.30) that explained 5.24-20.31% of the phenotypic variance. With the linkage disequilibrium r2 > 0.2, these significant associations were binned into 40 quantitative trait loci (QTL) clusters. Among them, 14 important QTL clusters were discovered in two environments and/or with phenotypic contributions greater than 10%. By analyzing the genomic regions within 100 kb upstream and downstream of the peak SNPs within the 14 loci, 334 annotated genes were found. Among these, 32 genes were potentially associated with root development according to their expression analysis. Furthermore, the protein interaction network using the 334 annotated genes gave nine genes involved in a substantial number of interactions, including a key gene associated with root development, BnaC09g36350D. This research provides the groundwork for deciphering B. napus' genetic variations and improving its root system architecture.