Abstract
Caffeic acid O-methyltransferases (COMTs) play an essential role in lignin synthesis procession, especially in the plant’s phenylalanine metabolic pathway. The content of COMT genes in cotton and the relationship between their expression patterns have not been studied clearly in cotton. In this study, we have identified 190 COMT genes in cotton, which were classified into three groups (I, II and III), and mapped on the cotton chromosomes. In addition, we found that 135 of the 190 COMT genes result from dispersed duplication (DSD) and whole-genome duplication (WGD), indicating that DSD and WGD were the main forces driving COMT gene expansion. The Ka/Ks analysis showed that GhCOMT43 and GhCOMT41 evolved from GaCOMT27 and GrCOMT14 through positive selection. The results of qRT-PCR showed that GhCOMT13, GhCOMT28, GhCOMT39 and GhCOMT55 were related to lignin content during the cotton fiber development. GhCOMT28, GhCOMT39, GhCOMT55, GhCOMT56 and GhCOMT57 responded to Verticillium Wilt (VW) and maybe related to VW resistance through lignin synthesis. Conclusively, this study found that GhCOMTs were highly expressed in the secondary wall thickening stage and VW. These results provide a clue for studying the functions of GhCOMTs in the development of cotton fiber and VW resistance and could lay a foundation for breeding cotton cultivates with higher quantity and high resistance to VW.
Highlights
Cotton (Gossypium) is currently one of the most important economic crops globally, and it occupies a vitally important position in economy of the China
Upland cotton has 57 Caffeic acid O-methyltransferases (COMTs) genes members named GhCOMT1~GhCOMT57; G. barbadense has the most genes and are named GbCOMT1~GbCOMT60; G. arboretum COMT members are named as GaCOMT1~GaCOMT35; and G. raimondii COMTs are named GrCOMT1~GrCOMT35 (Additional file 1: Table S3)
The codin sequence lengths of these genes were between 720 bp (GhCOMT11) to 1158 bp (GhCOMT50); they coded 239 (GhCOMT11) to 385 (GhCOMT50) amino acid molecules; their relative molecular masses were between 26.81 kD (GhCOMT11) and 43.30 kD (GhCOMT50); and the isoelectric points of these proteins ranged between 4.745 (GhCOMT8) and 7.553 (GhCOMT27)
Summary
Cotton (Gossypium) is currently one of the most important economic crops globally, and it occupies a vitally important position in economy of the China. Cotton fiber is an essential natural plant fiber with high applications in the modern textile industry [1]. Cotton fiber is developed from the single cell of ovule epidermis, and it is the most extended plant cell found so far, which is different from the general phloem fiber [2]. The process of cotton fiber development can be divided into five stages: fiber initiation stage (−3 DPA– 3 DPA), rapid cell growth stage (primary wall synthesis) (2–20 DPA), transitional period (16–20 DPA), secondary wall thickening stage (16~45DPA) and dehydration maturity stage (45–50 DPA) [3,4]. The cotton fiber is mainly made of cellulose, which account for 93–95% of the dry weight, and the rest are companions of the fiber [5]. Cotton fiber is important for studying cell elongation and cell wall growth of cotton
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