Isolation and analyses of genes preferentially expressed during early cotton fiber development by subtractive PCR and cDNA array

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Abstract
Cotton fibers are differentiated epidermal cells originating from the outer integuments of the ovule. To identify genes involved in cotton fiber elongation, we performed subtractive PCR using cDNA prepared from 10 days post anthesis (d.p.a.) wild‐type cotton fiber as tester and cDNA from a fuzzless‐lintless (fl) mutant as driver. We recovered 280 independent cDNA fragments including most of the previously published cotton fiber‐related genes. cDNA macroarrays showed that 172 genes were significantly up‐regulated in elongating cotton fibers as confirmed by in situ hybridization in representative cases. Twenty‐nine cDNAs, including a putative vacuolar (H+)‐ATPase catalytic subunit, a kinesin‐like calmodulin binding protein, several arabinogalactan proteins and key enzymes involved in long chain fatty acid biosynthesis, accumulated to greater than 50‐fold in 10 d.p.a. fiber cells when compared to that in 0 d.p.a. ovules. Various upstream pathways, such as auxin signal transduction, the MAPK pathway and profilin‐ and expansin‐induced cell wall loosening, were also activated during the fast fiber elongation period. This report constitutes the first systematic analysis of genes involved in cotton fiber development. Our results suggest that a concerted mechanism involving multiple cellular pathways is responsible for cotton fiber elongation.