Abstract
To investigate the molecular mechanisms of fiber initiation in cotton (Gossypium spp.), an integrated approach combining transcriptome, iTRAQ-based proteome and genetic mapping was taken to compare the ovules of the Xuzhou 142 wild type (WT) with its fuzzless-lintless (fl) mutant at −3 and 0 day post-anthesis. A total of 1,953 mRNAs, 187 proteins, and 131 phosphoproteins were differentially expressed (DE) between WT and fl, and the levels of transcripts and their encoded proteins and phosphoproteins were highly congruent. A functional analysis suggested that the abundance of proteins were mainly involved in amino sugar, nucleotide sugar and fatty acid metabolism, one carbon pool for folate metabolism and flavonoid biosynthesis. qRT-PCR, Western blotting, and enzymatic assays were performed to confirm the regulation of these transcripts and proteins. A molecular mapping located the lintless gene li3 in the fl mutant on chromosome 26 for the first time. A further in-silico physical mapping of DE genes with sequence variations between fl and WT identified one and four candidate genes in the li3 and n2 regions, respectively. Taken together, the transcript abundance, phosphorylation status of proteins at the fiber initiation stage and candidate genes have provided insights into regulatory processes underlying cotton fiber initiation.
Highlights
Was originally discovered in a commercial Upland cultivar Xuzhou 1428
Ovules were collected at − 3 and 0 DPA to identify differentially expressed genes (DEGs) or differentially expressed proteins/phosphoproteins (DEPs) between WT and its fl mutant by RNA-Seq and iTRAQ technology
Cotton fiber initiation is a faultlessly irreversible, concerted process involving a range of morphological, physiological, and molecular changes that result in the development of a soft fiber with attributes desirable to humans
Summary
Was originally discovered in a commercial Upland cultivar Xuzhou 1428. Subsequent studies determined that the mutant is controlled by two pairs of recessive genes with a genotype of li3li3n2n2. Kwak et al studied significantly differentially expressed microRNAs (miRNAs) between Xuzhou 142 and fl mutant ovules (1 to 10 DPA) They discovered that 8 miRNAs were up-regulated in the WT, suggesting that miRNAs potentially regulate transcripts in cotton fiber development[16]. Wang et al investigated fiber-initiation-related miRNAs between Xuzhou 142 and fl ovules (−3 to 3 DPA) and found 12 up-regulated miRNAs in the WT17 These results indicate that cotton fiber differentiation and initiation is a complicated biological process requiring a series of well-orchestrated changes in gene regulation of various physiological and biochemical pathways. A co-localisation of anchoring markers with the predicted genes in the li[3] and n2 regions allowed the identification of possible candidate genes with differential expression and sequence variation for the two genes These results provide a foundation to isolate and clone li[3] and n2 genes and elucidating their functional roles in cotton
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