Comparative Analysis of Fiber Morphogenesis Genes of Calotropis procera and Gossypium hirsutum

Cotton (Gossypium spp.) is the leading fiber crop in the world. The earnings from fiber lint are associated with its quality traits. For studying the major fiber development specific genes, cDNA libraries were used to establish 1000 EST's (expressed sequence tags), each from the fast-growing fibers of Calotropis procera and Gossypium hirsutum L. Most abundantly expressed transcripts of C. procera coded for expansins, aquaporins and sugar/salt transporters. Four homologs of expansin gene (CpEXPA1, CpEXPA2, CpEXPA3 and CpEXPA4) and four of aquaporins (CpTiP1, CpTiP2, CpPiP1 and CpPiP2) were found to be the most abundantly expressed transcripts in fast growing C. procera fiber cells. Cotton fiber EST's revealed two homologs of expansin, one for G. hirsutum plasma membrane intrinsic protein (GhPiP1) and one transcript for sucrose synthase. The GhPiP1 had 70% amino acid identity to CpPiP1, while no homolog was detected for CpPiP2 in cotton fibers. Real-time PCR data showed that CpPiP1 had about 40% higher transcript level of the gene in C. procera as compared to cotton. CpPiP2 showed high level of transcripts in C. procera fiber only. On the other hand, CpEXPA3 was the closest homologue of GhEXP15 (76% amino acid identity) and its transcript level was 80% higher in C. procera fibers. Expression of sucrose synthase was at its high level in 5-15 DPA cotton fibers. These studies demonstrated that CpPiP2, CpEXPA3 and sucrose synthase are the best candidate genes for fiber modification in G. hirsutum. (C) 2018 Friends Science Publishers