Cotton is a major fiber and oil crop worldwide. Cotton production, however, is often threatened by abiotic environmental stresses. GRAS family proteins are among the most abundant transcription factors in plants and play important roles in regulating root and shoot development, which can improve plant resistance to abiotic stresses. However, few studies on the GRAS family have been conducted in cotton. Recently, the G. hirsutum genome sequences have been released, which provide us an opportunity to analyze the GRAS family in G. hirsutum. In total, 150 GRAS proteins from G. hirsutum were identified. Phylogenetic analysis showed that these GRAS protins could be classified into 14 subfamilies including SCR, DLT, OS19, LAS, SCL4/7, OS4, OS43, DELLA, PAT1, SHR, HAM, SCL3, LISCL and G_GRAS. The gene structure and motif distribution analysis of the GRAS members in G. hirsutum revealed that many genes of the SHR subfamily have more than one intron, which maybe a kind of form in the evolution of plant by obtaining or losing introns. Chromosomal location and duplication analysis revealed that segment and tandem duplication maybe the reasons of the expension of the GRAS family in cotton. Gene expression analysis confirmed the expression level of GRAS members were up-regulated under different abiotic stresses, suggesting that their possible roles in response to stresses. What’s more, higher expression level in root, stem, leaf and pistil also indicated these genes may have effect on the development and breeding of cotton. This study firstly shows the comprehensive analysis of GRAS members in G. hirsutum. Our results provide important information about GRAS family and a framework for stress-resistant breeding in G. hirsutum.

Verticillium dahliae is a phytopathogenic fungal pathogen that causes vascular wilt diseases responsible for considerable decreases in cotton yields. The complex mechanism underlying cotton resistance to Verticillium wilt remains uncharacterized. Identifying an endogenous resistance gene may be useful for controlling this disease. We cloned the ribosomal protein L18 (GaRPL18) gene, which mediates resistance to Verticillium wilt, from a wilt-resistant cotton species (Gossypium arboreum). We then characterized the function of this gene in cotton and Arabidopsis thaliana plants. GaRPL18 encodes a 60S ribosomal protein subunit important for intracellular protein biosynthesis. However, previous studies revealed that some ribosomal proteins are also inhibitory toward oncogenesis and congenital diseases in humans and play a role in plant disease defense. Here, we observed that V. dahliae infections induce GaRPL18 expression. Furthermore, we determined that the GaRPL18 expression pattern is consistent with the disease resistance level of different cotton varieties. GaRPL18 expression is upregulated by salicylic acid (SA) treatments, suggesting the involvement of GaRPL18 in the SA signal transduction pathway. Virus-induced gene silencing technology was used to determine whether the GaRPL18 expression level influences cotton disease resistance. Wilt-resistant cotton species in which GaRPL18 was silenced became more susceptible to V. dahliae than the control plants because of a significant decrease in the abundance of immune-related molecules. We also transformed A. thaliana ecotype Columbia (Col-0) plants with GaRPL18 according to the floral dip method. The plants overexpressing GaRPL18 were more resistant to V. dahliae infections than the wild-type Col-0 plants. The enhanced resistance of transgenic A. thaliana plants to V. dahliae is likely mediated by the SA pathway. Our findings provide new insights into the role of GaRPL18, indicating that it plays a crucial role in resistance to cotton “cancer”, also known as Verticillium wilt, mainly regulated by an SA-related signaling pathway mechanism.

Brassinosteroids (BRs) play crucial roles in drought tolerance, but the underlying molecular mechanisms remain unclear in the important oilseed and fiber crop, cotton (Gossypium hirsutum L.). To elucidate how BRs mediate drought tolerance in cotton, a cotton brassinosteroid (BR)-deficient mutant, pag1 (pagoda1), was employed for analysis. Importantly, the pag1 mutant showed increased sensitivity to drought stress, with shorter primary roots and fewer lateral roots. The number of stomata was significantly increased in the mutant, and the stomata aperture was much wider than that of the control plants. These mutant plants therefore showed an increased water loss rate. Furthermore, the abscisic acid (ABA) content, photosynthetic efficiency and starch content of the mutant were significantly lower than those of the wild type. The overall performance of the mutant plants was worse than that of the wild-type control under both normal and drought conditions. Moreover, Proteomic analysis revealed reduced levels of stress-related proteins in pag1 plants. These results suggest that BRs may modulate the drought tolerance of cotton by regulating much genes that related to drought stress and multiple organ responses to drought, including root growth, stomata development, the stomata aperture and photosynthesis. This study provides an important basis for understanding drought resistance regulated by BRs and cultivating drought-resistant cotton lines.

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, has become one of the most serious diseases that damage wheat. The TaPFT (pore-forming toxin-like) and TaHRC (histidine-rich calcium-binding protein) genes at the quantitative trait locus Fhb1 were identified to confer resistance to FHB in the wheat cultivar Sumai 3. In this study, a wheat ricin B-like lectin gene (designated TaRBL) that interacted with TaPFT was isolated by a yeast two-hybrid screen of a wheat cDNA library. A yeast two-hybrid and bimolecular fluorescence complementation study further verified that TaRBL interacted with TaPFT but not with TaHRC. Gene expression studies showed that upon F. graminearum infection, TaRBL expression was upregulated in resistant cultivars but downregulated in susceptible cultivars. Furthermore, knockdown of TaRBL expression by barley stripe mosaic virus-induced gene silencing significantly reduced the resistance of wheat to FHB in both the resistant cultivar Sumai 3 and the susceptible cultivar Jimai 22. Thus, we conclude that TaRBL encodes a ricin B-like lectin protein that interacts with TaPFT and is involved in resistance to FHB in wheat.