Genome-wide identification and characterization of ALTERNATIVE OXIDASE genes and their response under abiotic stresses in Camellia sinensis (L.) O. Kuntze

Abstract

Four typical ALTERNATIVE OXIDASE genes have been identified in tea plants, and their sequence features and gene expression profiles have provided useful information for further studies on function and regulation. Alternative oxidase (AOX) is a terminal oxidase located in the respiratory electron transport chain. AOX catalyzes the oxidation of quinol and the reduction of oxygen into water. In this study, a genome-wide search and subsequent DNA cloning were performed to identify and characterize AOX genes in tea plant (Camellia sinensis (L.) O. Kuntze cv. Longjing43). Our results showed that tea plant possesses four AOX genes, i.e., CsAOX1a, CsAOX1d, CsAOX2a and CsAOX2b. Gene structure and protein sequence analyses revealed that all CsAOXs share a four-exon/three-intron structure with highly conserved regions and amino acid residues, which are necessary for AOX secondary structures, catalytic activities and post-translational regulations. All CsAOX were shown to localize in mitochondria using the green fluorescent protein (GFP)-targeting assay. Both CsAOX1a and CsAOX1d were induced by cold, salt and drought stresses, and with different expression patterns in young and mature leaves. Reactive oxygen species (ROS) accumulated strongly after 72 and 96 h cold treatments in both young and mature leaves, while the polyphenol and total catechin decreased significantly only in mature leaves. In comparison to AtAOX1a in Arabidopsis thaliana, CsAOX1a lost almost all of the stress-responsive cis-acting regulatory elements in its promoter region (1500 bp upstream), but possesses a flavonoid biosynthesis-related MBSII cis-acting regulatory element. These results suggest a link between CsAOX1a function and the metabolism of some secondary metabolites in tea plant. Our studies provide a basis for the further elucidation of the biological function and regulation of the AOX pathway in tea plants.

(+)‐Catechin, epicatechin and epigallocatechin gallate are important inducible defensive compounds against Ectropis grisescens in tea plants

“…Analyses were carried out with a high‐performance liquid chromatography system (Waters e2695 Separations Module). For more details, please refer to Ding et al (2018). The content of each compound was quantified using an external standard curve.…”

Carrot AOX2a Transcript Profile Responds to Growth and Chilling Exposure

“…The involvement of different signaling pathways in AOX induction have been reported [50] and the role of the promoter region in driving that expression has been investigated at different levels [51][52][53][54]. The role of cis-acting regulatory elements (CAREs) located within the promoter sequence of AOX genes has been demonstrated by driving the expression of reporter genes using promoter deletion constructs [51,52]), by mutagenesis studies [53], and more recently by comparative analysis following in silico bioinformatics studies [54,55].…”