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

Cotton fiber is an ideal model for studying plant cell elongation. To date, the underlying mechanisms controlling fiber elongation remain unclear due to their high complexity. In this study, a comparative proteomic analysis between a short-lint fiber mutant (Ligon lintless, Li1) and its wild-type was performed to identify fiber elongation-related proteins. By 2-DE combined with local EST database-assisted MS/ MS analysis, 81 differentially expressed proteins assigned to different functional categories were identified from Li1 fibers, of which 54 were down-regulated and 27 were up-regulated. Several novel aspects regarding cotton fiber elongation can be illustrated from our data. First, over half of the downregulated proteins were newly identified at the protein level, which is mainly involved in protein folding and stabilization, nucleocytoplasmic transport, signal transduction, and vesicular-mediated transport. Second, a number of cytoskeleton-related proteins showed a remarkable decrease in protein abundance in the Li1 fibers. Accordingly, the architecture of actin cytoskeleton was severely deformed and the microtubule organization was moderately altered, accompanied with dramatic disruption of vesicle trafficking. Third, the expression of several proteins involved in unfolded protein response (UPR) was activated in Li1 fibers, indicating that the deficiency of fiber cell elongation was related to ER stress. Collectively, these findings significantly advanced our understanding of the mechanisms associated with cotton fiber elongation.