J Syst Evol ›› 2021, Vol. 59 ›› Issue (2): 326-340.DOI: 10.1111/jse.12537

• Research Articles • Previous Articles     Next Articles

Insights into the origin and evolution of plant sigma factors

Xin-Xing Fu1,2, Jian Zhang1*, Guo-Qiang Zhang3, Zhong-Jian Liu4,5,6, and Zhi-Duan Chen1,7   

  1. 1State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
    3Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China
    4Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at the College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou 350002, China
    5College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510640, China
    6Fujian Colleges and Universities and Engineering Research Institute of Conservation and Utilization of Natural Bioresources, College of Forestry, Fujian Agriculture and Forestry University, Fuzhou 350002, China
    7Sino‐Africa Joint Research Center, Chinese Academy of Sciences, Wuhan 430074, China
  • Received:2019-05-01 Accepted:2019-08-19 Online:2019-08-26 Published:2021-03-01

Abstract: Plant sigma factors (SIGs) are key regulators of chloroplast gene expression and chloroplast differentiation. Despite their functional importance, the evolutionary history of these factors remains unclear. Using newly available genomic and transcriptomic data, we undertook a detailed and comprehensive phylogenetic analysis of SIG homologues from land plants and algae. Our results reveal that plants have acquired sigma factors from ancestor cyanobacteria through endosymbiotic gene transfers, forming four major clades, namely, super‐SIG2 (SIG2/3/4/6/SIG2‐like), SIG1, SIG5, and SIGX. The super‐SIG2 clade was confirmed to have evolved from cyanobacterial SIGA factors, and a novel clade (SIGX) specific to non‐angiosperms was revealed here. Gene duplications (mainly whole genome duplications) within lineages and species have contributed to the expansion of sigma factors in plants, especially flowering plants. We hypothesize that plant sigma factors originated from different endosymbiotic ancestors and evolved diverse functions. This not only sheds new light on the evolution of plant SIG genes but also paves the way for understanding the functional diversification of these genes.

Key words: chloroplast, evolution, gene duplication, phylogenetic analysis, sigma factor