Cloning and Characterization of a CAP Gene Expressed in Gossypium arboreum Fuzzless Mutant

Abstract

The adenylyl cyclase‐associated protein (CAP) was first identified in the budding yeast as a protein that functions in cytoskeletal organization and signal transduction. We isolated two CAP homologs from wild‐type cotton Gossypium arboreum L. (DPL971) and its natural fuzzless mutant (DPL972). Alignments of 3998‐bp genomic and 1425‐bp cDNA sequences revealed that the cap genes contain nine introns and an open reading frame (ORF) encoding a 471 amino acid protein. The predicted amino acid sequence shares high identity (∼70%) with Arabidopsis thaliana, Medicago truncatula, and Oryza sativa Expression profiles of the gene were studied from ovule, leaf, hypocotyl, and root tissues, through reverse transcriptase polymerase chain reaction and Northern blotting analysis. The results revealed that the gene was expressed in all tissues tested in wild‐type and fuzzless plants. The expression of GaCAP reached the highest level in both wild‐type and mutant fibers during 1 to 4 d postanthesis (DPA), then gradually declined in the mutant after 4 DPA. By comparing the predicted amino acid sequences, a polar substitution was observed at a conserved position between wild‐type and mutant. At this position, the conserved uncharged unpolar alanine (amino acid 44) of GaCAP was replaced by a polar threonine in GaCAPm. Therefore, our results suggest that GaCAP may play a functional role during early stages of cotton fiber development.