Location: Cotton Fiber Bioscience ResearchTitle: Functional divergence of cellulose synthase orthologs in between wild Gossypium raimondii and domesticated G. arboreum diploid cotton species
|SONG, XIANLIANG - Shandong Agricultural University|
|Delhom, Christopher - Chris|
Submitted to: Cellulose
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2019
Publication Date: 11/18/2019
Citation: Kim, H.J., Thyssen, G.N., Song, X., Delhom, C.D., Liu, Y. 2019. Functional divergence of cellulose synthase orthologs in between wild Gossypium raimondii and domesticated G. arboreum diploid cotton species. Cellulose. 26:9483-9501. https://doi.org/10.1007/s10570-019-02744-y.
Interpretive Summary: Cellulose is a major component of cotton fibers and determines quality and commercial values of raw fibers. Despite cellulose synthase (CESA) is a major gene producing cellulose in cotton fibers, it has not been characterized which CESA genes contribute to fiber length or thickening processes due to technical difficulties of distinguishing individual CESA gene among the CESA family genes sharing high sequence similarity. In this study, we used two advanced genomic techniques as well as comprehensive phenotypic analyses for distinguishing each CESA gene, and compared their expression patterns between wild and cultivated cotton species differing in fiber properties and morphologies. The CESA genes in the cultivated cotton species with high fiber quality showed more tissue-dependent and less redundant expression patterns as compared to those in the wild cotton species with low fiber quality. This discovery provides insight on how cellulose biosynthesis is regulated by different CESA genes and will allow cotton breeders to better understand and improve cotton fiber properties.
Technical Abstract: Cellulose synthase (CESA) is a major gene family that synthesizes the primary and secondary cell wall (PCW and SCW) cellulose providing flexibility and mechanical strength in plant cells. Developmental regulation of various CESA genes involved in PCW and SCW cellulose biosynthesis is critical for plant cell wall expansion and thickening. Despite the important CESA functions in cotton plants in which mature fibers are composed of nearly pure cellulose, functional divergence of cotton CESA genes has not been well characterized due to the technical difficulties of distinguishing individual CESA family genes that share high sequence similarity. Therefore, we determined the expression levels and patterns of CESA orthologous pairs from two diploid cotton species, wild Gossypium raimondii and domesticated G. arboreum, and compared functional divergence of the CESA genes using RNAseq and a PCR technique with enhanced specificity to distinguish single nucleotide polymorphisms (SNPs) between the CESA orthologues. The RNAseq method was neither able to identify pseudo CESA genes nor distinguish the PCW CESA genes that share nearly identical sequence. In contrast, the enhanced PCR method enabled identification of pseudogenes, and showed differential regulation patterns between PCW and SCW CESA genes that were consistent with the cellulose content and developmental stages determined by comprehensive phenotypic analyses. Furthermore, it demonstrated substantial expression divergence of CESA orthologues between wild and domesticated cotton species differing in fiber properties and morphologies. Our results support the notion that subfuctionalization positively contributed to the fiber properties of G. arboreum during domestication by altering CESA expression levels and patterns. This discovery provides insight on how cellulose biosynthesis is regulated by different CESA genes and will allow cotton breeders to better understand and improve cotton fiber properties.