Abstract
Plant type III polyketide synthase (PKS) can catalyse the formation of a series of secondary metabolites with different structures and different biological functions; the enzyme plays an important role in plant growth, development and resistance to stress. At present, the PKS gene has been identified and studied in a variety of plants. Here, we identified 11 PKS genes from upland cotton (Gossypium hirsutum) and compared them with 41 PKS genes in Populus tremula, Vitis vinifera, Malus domestica and Arabidopsis thaliana. According to the phylogenetic tree, a total of 52 PKS genes can be divided into four subfamilies (I–IV). The analysis of gene structures and conserved motifs revealed that most of the PKS genes were composed of two exons and one intron and there are two characteristic conserved domains (Chal_sti_synt_N and Chal_sti_synt_C) of the PKS gene family. In our study of the five species, gene duplication was found in addition to Arabidopsis thaliana and we determined that purifying selection has been of great significance in maintaining the function of PKS gene family. From qRT-PCR analysis and a combination of the role of the accumulation of proanthocyanidins (PAs) in brown cotton fibers, we concluded that five PKS genes are candidate genes involved in brown cotton fiber pigment synthesis. These results are important for the further study of brown cotton PKS genes. It not only reveals the relationship between PKS gene family and pigment in brown cotton, but also creates conditions for improving the quality of brown cotton fiber.
Highlights
Plant polyketone compounds are secondary metabolites having a cyclic structure with an oxygen atom bound to the carbon ring
III contained three species (Gossypium hirsutum, Populus tremula and Malus domestica), while subfamily II only consisted of Vitis vinifera
We identified and compared 11 sequences of polyketide synthase (PKS) protein in upland cotton with the sequences of Oryza sativa chalcone synthase (OsCHS), Arabidopsis thaliana chalcone synthase (AtCHS) and Medicago sativa chalcone synthase (MsCHS) to clarify the functional divergence of PKS III gene family members
Summary
Plant polyketone compounds are secondary metabolites having a cyclic structure with an oxygen atom bound to the carbon ring. This group includes phenols, stilbene and flavonoid compounds (Abe & Morita, 2010). Owing to the complexity and variety of the pathways and mechanisms of biosynthesis, the number of polyketone compounds is very large and their molecular structures are complex. This complexity results in the compounds having prominent and varied biological activities (Austin & Noel, 2002). According to the structure of the protein, PKS can be divided into PKS I, II and III
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