Evolution of pectin-synthesis-relevant galacturonosyltransferase gene family and its expression during cotton fiber development

Abstract Background: Pectin is a key substance involved in cell wall development, and the galacturonosyltransferases (GAUTs) gene family is a critical participant in the pectin synthesis pathway. Systematic and comprehensive research on GAUTs has not been performed in cotton. Analysis of the evolution and expression patterns of the GAUT gene family in different cotton species is needed to increase knowledge of the function of pectin in cotton fiber development.Results: In this study, we identified 131 GAUT genes in the genomes of four Gossypium species (G. raimondii, G. barbadense, G. hirsutum, and G. arboreum), and classified them as GAUT-A, GAUT-B and GAUT-C. Among them, 15 GAUT genes encoded proteins (GAUT1 to GAUT15). All GAUT family genes except for the gene GAUT7 coding contained a consevrved Glyco_transf_8 domain (H-DN-A-SVV-S-V-H-T-F). The consevrved sequences of GAUT7 was a PLN (phospholamban) 02769 domain, categorized as a probable galacturonosyltransferase. According to cis-elemet analysis, GAUT genes expression may be regulated by hormones such as JA, GA, SA, ABA, Me-JA and IAA. The evolution and expression patterns of the GAUT gene family in different cotton species and the expression levels in upland cotton materials having different fiber strengths were analyzed. Peak expression of GhGAUT genes was observed before 15DPA; in the six materials with high fiber strength, the expression was concentrated from 10 to 15DPA; while the highest expression in low fiber strength materials was detected between 5 and 10 DPA. The results presented in this paper lays the foundation for future research on gene function during cotton fiber development.Conclusions: The GAUT gene family may affect cotton fiber development, including fiber elongation and fiber thickening. In the low-strength-fiber lines, GAUTs mainly participate in fiber elongation, whereas their major effect on cotton with high-strength fiber is related to both elongation and thickening.