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SUMMARY: Drought has a severe impact on the quality and yield of cotton. Deciphering the key genes related to drought tolerance is important for understanding the regulation mechanism of drought stress and breeding drought‐tolerant cotton cultivars. Several studies have demonstrated that NAC transcription factors are crucial in the regulation of drought stress, however, the related functional mechanisms are still largely unexplored. Here, we identified that NAC transcription factor GhNAC4 positively regulated drought stress tolerance in cotton. The expression of GhNAC4 was significantly induced by abiotic stress and plant hormones. Silencing of GhNAC4 distinctly impaired the resistance to drought stress and overexpressing GhNAC4 in cotton significantly enhanced the stress tolerance. RNA‐seq analysis revealed that overexpression of GhNAC4 enriched the expression of genes associated with the biosynthesis of secondary cell walls and ribosomal proteins. We confirmed that GhNAC4 positively activated the expressions of GhNST1, a master regulator reported previously in secondary cell wall formation, and two ribosomal protein‐encoding genes GhRPL12 and GhRPL18p, by directly binding to their promoter regions. Overexpression of GhNAC4 promoted the expression of downstream genes associated with the secondary wall biosynthesis, resulting in enhancing secondary wall deposition in the roots, and silencing of GhRPL12 and GhRPL18p significantly impaired the resistance to drought stress. Taken together, our study reveals a novel pathway mediated by GhNAC4 that promotes secondary cell wall biosynthesis to strengthen secondary wall development and regulates the expression of ribosomal protein‐encoding genes to maintain translation stability, which ultimately enhances drought tolerance in cotton. Significance Statement: Drought is a big threat to cotton production worldwide. This study identifies that GhNAC4, a member of the NAC family, acts upstream of GhNST1, GhRPL12, and GhRPL18p, modulates secondary cell wall biosynthesis and expression of ribosomal protein genes, and enhances plant drought tolerance in cotton. [ABSTRACT FROM AUTHOR]

β-1,3-glucanase functions in plant physiological and developmental processes. However, how β-1,3-glucanase participates in cell wall development remains largely unknown. Here, we answered this question by examining the role of GhGLU18, a β-1,3-glucanase, in cotton (Gossypium hirsutum) fibers, in which the content of β-1,3-glucan changes dynamically from 10% of the cell wall mass at the onset of secondary wall deposition to <1% at maturation. GhGLU18 was specifically expressed in cotton fiber with higher expression in late fiber elongation and secondary cell wall (SCW) synthesis stages. GhGLU18 largely localized to the cell wall and was able to hydrolyze β-1,3-glucan in vitro. Overexpression of GhGLU18 promoted polysaccharide accumulation, cell wall reconstruction, and cellulose synthesis, which led to increased fiber length and strength with thicker cell walls and shorter pitch of the fiber helix. However, GhGLU18-suppressed cotton resulted in opposite phenotypes. Additionally, GhGLU18 was directly activated by GhFSN1 (fiber SCW-related NAC1), a NAC transcription factor reported previously as the master regulator in SCW formation during fiber development. Our results demonstrate that cell wall–localized GhGLU18 promotes fiber elongation and SCW thickening by degrading callose and enhancing polysaccharide metabolism and cell wall synthesis. A cell wall–localized β-1,3-glucanase enhances polysaccharide metabolism and cell wall synthesis to promote fiber cell elongation and thickening. [ABSTRACT FROM AUTHOR]

In recent years, microorganisms such as algae have been found on composite and RTV coated insulators in humid environment in southwest and southern China. Algae growth poses a potential threat to the outer insulation of electrical power system because of the special features of biological foul. Insulator samples with algae growth were obtained from transmission towers of 500 kV Tianguang DC transmission line and the influence of algae growth on the external insulation performance was studied in this paper. A measurement circuit was used to measure the partial surface conductivity of algae and non-algae dots on insulator surfaces. Water spray classification method was used to test the hydrophobicity of algae and non-algae parts of the insulators. An image processing method was proposed to discern algae on the insulator surfaces and calculate the algae coverage rate. The withstand capability of insulator were tested at working voltage and 1.2 times working voltage. The research results showed that the presence of algae increased the local salt distribution and reduced the hydrophobicity of insulator surfaces. The results also indicated that impacts of algae contanmination to withstand capability of insulators were limited when the algae coverage rate was less than 20%. [ABSTRACT FROM AUTHOR]