The cotton XLIM protein (GhXLIM6) is required for fiber development via maintaining dynamic F‐actin cytoskeleton and modulating cellulose biosynthesis

Abstract

N.-N.W. contributed equally to this work.SUMMARY LIM domain proteins are cysteine-rich proteins, and are often considered as actin bundlers and transcription factors in plants. However, the roles of XLIM proteins in plants (especially in cotton) remain unexplored in detail so far. In this study, we identified a cotton XLIM protein (GhXLIM6) that is preferentially expressed in cotton fiber during whole elongation stage and early secondary cell wall (SCW) synthesis stage. The GhXLIM6-silenced transgenic cotton produces shorter fibers with thinner cell walls, compared with wildtype (WT). GhXLIM6 protein could directly bind F-actin and promote actin polymerization both in vitro and in vivo. It also acts as a transcription factor to suppress GhKNL1 expression through binding the PAL-box element of GhKNL1 promoter, and subsequently regulate the expression of CesA genes related to cellulose biosynthesis and deposition in SCWs of cotton fibers. The cellulose content in fibers of GhXLIM6 RNAi cotton is lower than that in WT. Taken together, these data reveal the dual roles of GhXLIM6 in fiber development. On one hand, GhXLIM6 functions in fiber elongation through binding to F-actin to maintain the dynamic F-actin cytoskeleton. On the other hand, GhXLIM6 fine-tunes fiber SCW formation, probably through directly suppressing transcription of GhKNL1 to promote cellulose biosynthesis.

G65V Substitution in Actin Disturbs Polymerization Leading to Inhibited Cell Elongation in Cotton

“…There is a distinct rearrangement of the actin cytoskeleton during transition from fiber elongation to secondary wall deposition (Seagull, 1990; Wang et al, 2010). In line with the cytological observations, a variety of ABP encoding genes have been found to be preferentially expressed in developing fiber cells, such as those encoding actin deploymerizing factors (Wang et al, 2009), profilins (Wang et al, 2005; Wang et al, 2010; Bao et al, 2011), and LIM-domain proteins (Han et al, 2013; Li et al, 2013; Li et al, 2018). Moreover, studies of transgenic cotton suggest that some increases in F-actin abundance are beneficial for fiber quality improvement (Wang et al, 2009; Han et al, 2013), and formation of the higher actin cytoskeleton structure plays a determinant role in the progression of developmental phases of cotton fibers (Wang et al, 2010; Zhang et al, 2017).…”

Gossypium Genomics: Trends, Scope, and Utilization for Cotton Improvement

“…This kind of integrated strategy efficiently isolated and validated several key genes with important functions. For instance, GhARF2, GhARF18 [52], GhXLIM6 [53], GhFSN1 [54], GhJAZ2 [55], GhFAnnxA [56], GhPAG1 [57], GhCETS [58], GhHSP24.7 [59,60], GhAAI66 [61], GhDsPTP3a [62], GhERF38 [63], GhABF2 [64], CRR1 [65], GhERF38 [63], GbSOBIR1 [66], and GhCPK33 [67], as well as other genes necessary for fiber development, growth, germination, gossypol, flowering, and resistance to abiotic and biotic stresses and diseases have been described.…”

Disequilibrium evolution of Fructose-1,6-bisphosphatase gene family leads to their functional biodiversity in Gossypium species

“…Cotton fiber is developed from the differentiation of a single ectodermic epidermal cell, and the fiber formation process can be divided into four distinct but partially overlapping periods: initiation, elongation (primary wall formation), secondary wall thickening, and dehydration maturity [19]. Many methods, including QTL identification [20][21][22], GWAS analysis [23][24][25][26], and functional gene identification [27][28][29], have been used to tackle the problems of fiber development and fiber quality formation. Studies have revealed that fiber development is a very complex process, with a large number of metabolic pathways providing material support, and thousands of specific genes being involved in expression regulation.…”