MOLECULAR ANALYSIS OF DEVELOPMENT TO IMPROVE COTTON FIBER
Location: Cotton Fiber Bioscience Research Unit
Title: Cloning and characterization of homeologous cellulose synthase catalytic subunit 2 genes from allotetraploid cotton (Gossypium hirsutum L.)
Submitted to: Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 8, 2011
Publication Date: February 25, 2012
Citation: Kim, H.J., Triplett, B.A., Zhang, H., Lee, M., Hinchliffe, D.J., Li, P., Fang, D.D. 2012. Cloning and characterization of homeologous cellulose synthase catalytic subunit 2 genes from allotetraploid cotton (Gossypium hirsutum L.). Gene. 494(2):181-189.
Interpretive Summary: Mature cotton fibers consist of nearly pure cellulose and the cotton fiber quality is affected by cellulose production. Molecular mechanisms regulating cellulose production have not been well-characterized in cotton fibers. We isolated genes and transcripts of two cellulose synthase catalytic subunits (GhCesA2-AT and GhCesA2-DT) that are essentially responsible for cellulose production in fibers. Previously, genes like GhCesA2-DT without consensus sequences for splice were suggested to be non-functional genes. However, our results showed that GhCesA2-DT without consensus sequences for splice was a functional gene that could produce functional transcripts. GhCesA2-AT and GhCesA2-DT appear to involve in regulating cotton fiber properties since these transcripts were more expressed in cotton fibers with higher fiber bundle strength than those with lower fiber bundle strength. Thus, the ability to manipulate the expression of cellulose synthases involved in cellulose production may lead to strategies for improving cotton fiber quality. The data are useful to plant cell wall researchers to understand cellulose production mechanisms.
Cellulose synthase catalytic subunits (CesAs) are the catalytic sites within a multisubunit complex for cellulose biosynthesis in plants. CesAs have been extensively studied in diploid plants, but are not well characterized in polyploid plants. Gossypium hirsutum is an allotetraploid cotton species producing over 90% of the world’s cotton fibers. Although G. hirsutum CesAs (GhCesAs) are responsible for cellulose production in cotton fiber, very limited numbers of GhCesA genes have been identified. Here, we report isolating and characterizing a pair of homeologous CesA2 genes and their full-length cDNAs from allotetraploid cotton . The GhCesA2-AT gene from the A-subgenome and GhCesA2-DT gene from the D-subgenome were screened from a G. hirsutum BAC library. These genes shared 92% sequence similarity throughout the entire sequence. The coding sequences were nearly identical, and the deduced amino acid sequences from GhCesA2-AT (1,039 amino acids) and GhCesA2-DT (1,040 amino acids) were identical except four amino acids, whereas the noncoding sequences showed divergence. Sequence analyses showed that all exons of GhCesA2-AT contained consensus splice donor dinucleotides, but one exon in GhCesA2-DT contained nonconsensus splice donor dinucleotides. Although the nonconsensus splice donor dinucleotides were previously suggested to be involved in alternative splice or pseudogenization, our results showed that a majority of GhCesA2-AT and GhCesA2-DT transcripts consisted of functional and full-length transcripts with little evidence for alternative mRNA isoforms in developing cotton fibers. Expression analyses showed that GhCesA2-AT and GhCesA2-DT shared common temporal and spatial expression patterns, and they were highly and preferentially expressed during the cellulose biosynthesis stage in developing cotton fibers. The observations of higher expression levels of both GhCesA2-AT and GhCesA2-DT in developing fibers of one near-isogenic line (NIL) with higher fiber bundle strength over the other NIL with lower fiber bundle strength suggested that the differential expression of genes associated with secondary cell wall cellulose biosynthesis in developing fiber might affect cotton fiber properties.