Abiotic and biotic stressors adversely affect plant survival, biomass generation, and crop yields.  As the global availability of arable land declines and the impacts of global warming intensify, such stressors may have increasingly pronounced effects on agricultural productivity.  Currently, researchers face the overarching challenge of comprehensively enhancing plant resilience to abiotic and biotic stressors.  The secondary cell wall plays a crucial role in bolstering the stress resistance of plants.  To increase plant resistance to stress through genetic manipulation of the secondary cell wall, we cloned a cell wall protein designated glycine-rich protein-like (GhGRPL) from cotton fibers, and found that it is specifically expressed during the period of secondary cell wall biosynthesis.  Notably, this protein differs from its Arabidopsis homolog, AtGRP, since its glycine-rich domain is deficient in glycine residues.  GhGRPL is involved in secondary cell wall deposition.  Upregulation of GhGRPL enhances lignin accumulation and, consequently, the thickness of the secondary cell walls, thereby increasing the plant’s resistance to abiotic stressors, such as drought and salinity, and biotic threats, including Verticillium dahliae infection.  Conversely, interference with GhGRPL expression in cotton reduces lignin accumulation and compromises that resistance.  Taken together, our findings elucidate the role of GhGRPL in regulating secondary cell wall development through its influence on lignin deposition, which, in turn, reinforces cell wall robustness and impermeability.  These findings highlight the promising near-future prospect of adopting GhGRPL as a viable, effective approach for enhancing plant resilience to abiotic and biotic stress factors.

 Cotton (Gossypium) is an important economic crop providing most of the natural fiber for the global textile industry.  The secondary cell wall (SCW) comprises the major dry weight of cotton fiber, and is a key determinant of cotton yield and quality.  In this study, a fiber-specific promoter, proFbl2A, was employed to control the expression of a fusion gene of phytoene synthase and 1-deoxy-D-xylulose-5-phosphate synthase (GhPSY2D and GhDXS6D, respectively) in cotton fibers of the SCW synthesis stage, resulting in higher carotenoid and abscisic acid (ABA) levels in the transgenic cotton fibers.  The SCW synthesis initiated earlier in the ABA-up-regulated cotton fibers than the wild-type control, along with the expression of SCW stage-specific genes and key SCW regulators.  Consistently, several positive bZIP transcription factors of ABA signaling (GhbZIP27b, GhbZIP37b, and GhbZIP66b), were found to bind to and activate the promoters of key SCW regulators (GhTCP4A, GhFSN1, and GhMYB7D).  Furthermore, these bZIPs could also interact with and promote the expression of two ethylene synthase genes (GhACS10 and GhACO3).  Our data demonstrated that enhancement of carotenoid and ABA could advance SCW initiation by activating key transcription factors, and promote SCW thickening via ethylene biosynthesis in cotton fibers.