Abstract
In plants, the NAC (NAM-ATAF1/2-CUC) family of proteins constitutes several transcription factors and plays vital roles in diverse biological processes, such as growth, development, and adaption to adverse factors. Tea, as a non-alcoholic drink, is known for its bioactive ingredients and health efficacy. Currently, knowledge about NAC gene family in tea plant remains very limited. In this study, a total of 45 CsNAC genes encoding NAC proteins including three membrane-bound members were identified in tea plant through transcriptome analysis. CsNAC factors and Arabidopsis counterparts were clustered into 17 subgroups after phylogenetic analysis. Conserved motif analysis revealed that CsNAC proteins with a close evolutionary relationship possessed uniform or similar motif compositions. The distribution of NAC family MTFs (membrane-associated transcription factors) among higher plants of whose genome-wide has been completed revealed that the existence of doubled TMs (transmembrane motifs) may be specific to fabids. Transcriptome analysis exhibited the expression profiles of CsNAC genes in different tea plant cultivars under non-stress conditions. Nine CsNAC genes, including the predicted stress-related and membrane-bound genes, were examined through qRT-PCR (quantitative real time polymerase chain reaction) in two tea plant cultivars, namely, ‘Huangjinya’ and ‘Yingshuang’. The expression patterns of these genes were investigated in different tissues (root, stem, mature leaf, young leaf and bud) and under diverse environmental stresses (drought, salt, heat, cold and abscisic acid). Several CsNAC genes, including CsNAC17 and CsNAC30 that are highly orthologous to known stress-responsive ANAC072/RD26 were identified as highly responsive to abiotic stress. This study provides a global survey of tea plant NAC proteins, and would be helpful for the improvement of stress resistance in tea plant via genetic engineering.
Highlights
Tea is a non-alcoholic drink known for its bioactive ingredients and health efficacy
The potential adversity resistance of plants is often determined by expressing stress-inducible genes that are regulated by specific transcription factors (TFs) [4]
Identification of NAC family members in tea plant According to the RNA-seq database, the annotated sequences with “NAC” and “NAM” were searched, and 120 NAC unigenes were obtained
Summary
Tea is a non-alcoholic drink known for its bioactive ingredients and health efficacy. Kuntze], which originated from the southwest region of China, had been cultivated and utilized for thousands of years, and is planted worldwide nowadays [1]. Tea plant often suffers from numerous detrimental environmental factors, such as extreme temperature, drought and salinity [2, 3]. Enhanced environmental receptivity may significantly help improve the yield and quality of tea plant. The potential adversity resistance of plants is often determined by expressing stress-inducible genes that are regulated by specific transcription factors (TFs) [4]. TFs widely exiting in plants regulate the expression of target genes by binding directly or indirectly with specific cis-regulatory elements
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