Suppression of Sucrose Synthase Gene Expression Represses Cotton Fiber Cell Initiation, Elongation, and Seed Development

Abstract

Cotton is the most important textile crop as a result of its long cellulose-enriched mature fibers. These single-celled hairs initiate at anthesis from the ovule epidermis. To date, genes proven to be critical for fiber development have not been identified. Here, we examined the role of the sucrose synthase gene ( Sus ) in cotton fiber and seed by transforming cotton with Sus suppression constructs. We focused our analysis on 0 to 3 days after anthesis (DAA) for early fiber development and 25 DAA, when the fiber and seed are maximal in size. Suppression of Sus activity by 70% or more in the ovule epidermis led to a fiberless phenotype. The fiber initials in those ovules were fewer and shrunken or collapsed. The level of Sus suppression correlated strongly with the degree of inhibition of fiber initiation and elongation, probably as a result of the reduction of hexoses. By 25 DAA, a portion of the seeds in the fruit showed Sus suppression only in the seed coat fibers and transfer cells but not in the endosperm and embryo. These transgenic seeds were identical to wild-type seeds except for much reduced fiber growth. However, the remaining seeds in the fruit showed Sus suppression both in the seed coat and in the endosperm and embryo. These seeds were shrunken with loss of the transfer cells and were Ͻ 5% of wild-type seed weight. These results demonstrate that Sus plays a rate-limiting role in the initiation and elongation of the single-celled fibers. These analyses also show that suppression of Sus only in the maternal seed tissue represses fiber development without affecting embryo development and seed size. Additional suppression in the endosperm and embryo inhibits their own development, which blocks the formation of adjacent seed coat transfer cells and arrests seed development entirely.

Proteomic Identification of Differentially Expressed Proteins in the Ligon lintless Mutant of Upland Cotton (Gossypium hirsutum L.)

“…Among them, a sucrose synthase gene (Sus), an actin gene (GhACT1), and a gene encoding a rate-limiting enzyme (GhDET2) in brassinosteroid (BR) biosynthesis were shown to be crucial for fiber elongation. [8][9][10] Although identification of these genes or proteins has made a substantial contribution to understanding the molecular basis of cotton fiber development, the underlying mechanisms that regulate fiber elongation are still unclear due to their high complexity.…”

Unraveling mechanisms of cell expansion linking solute transport, metabolism, plasmodesmtal gating and cell wall dynamics

“…1), GhVIN1, a major vacuolar invertase in cotton fiber, shows evidently higher expression level early in fiber elongation (0-10 DAA) matching high VIN activity observed in this stage. 12 Transgenic analyses revealed that suppression of GhSus expression reduced fiber length and cellulose content 10 and silencing GhVIN1 decreases fiber elongation. 12 These findings indicate that (1) GhSus play roles in both fiber elongation and cellulose biosynthesis through osmotic regulation and supplying UDPglucose as substrate for cellulose production and hexoses for generation of ATP as an energy source for a variety of transport and metabolic processes (2) GhVIN1 appears to be more specifically required for the formation and enlargement of the central vacuole, pivotal for early fiber elongation (see below).…”

“…Once taken up into the fiber cells, sucrose could be degraded into UDPglucose and fructose by sucrose synthesis (GhSus) in the cytoplasm 10 or hydrolyzed by acid invertase into glucose and fructose in the vacuole, thus doubling the osmotic contribution GhSUT1, GhKT1, GhEXP1 are genes encoding sucrose and K + transporter and expansin, respectively; 5 GhSus: sucrose synthase genes; 10,19 GhVIN1: vacuolar invertase gene; 12 GhPIPs and TIPs encode plasma membrane and tonoplast intrinsic proteins, respectively (Ashley J, Patrick Jw, Ruan YL, unpublished data); GhPEPC 1 and 2, and GhGluc1 are genes encoding phosphoenolpyruvate carboxylase 11 and β1, 3-glucanase, 9 respectively. PD: plasmodesmata.…”

“…10,11 However, little is known how osmotically active solutes are accumulated in the vacuole driving the influx of water for cell expansion. In this context, the recent discovery on the important role of vacuolar invertase (VIN) in cotton fiber and Arabidopsis root elongation 12 represents a major advance in our understanding of mechanisms controlling plant cell expansion.…”

The two domains of cotton WLIM1a protein are functionally divergent

“…Recently, significant progress has been made in large-scale identification of genes and proteins involved in fiber development, particularly of those related to fiber elongation and secondary wall deposition (Arpat et al, 2004;Cao, 2015;Gou et al, 2007;Jin et al, 2013;Shi et al, 2006;Zhao et al, 2010). Moreover, a number of fiber development-related genes have been structurally or functionally characterized (Han et al, 2013;Li et al, 2005;Pei, 2015;Ruan et al, 2003;Shan et al, 2014;Xu et al, 2013;Zhang et al, 2011). These studies have made important progress towards understanding the molecular mechanisms governing cotton fiber development.…”