Analysis of the HD-Zip I transcription factor family in <i>Salvia miltiorrhiza</i> and functional research of <i>SmHD-Zip12</i> in tanshinone synthesis
Yanhong Bai, Ying Zhou, Qiaoqi Lei, Yu Wang, Gaobin Pu, Zhenhua Liu, Xue Chen, Qian Liu
Abstract
Background The homeodomain-leucine zipper I (HD-Zip I) transcription factor is a plant-specific protein that plays an essential role in the abiotic stress response of plants. Research on the HD-Zip I family in Salvia miltiorrhiza is still lacking. Methods and Results In this study, a total of 25 SmHD-Zip I proteins were identified. Their characterizations, phylogenetic relationships, conserved motifs, gene structures, and cis-elements were analyzed comprehensively using bioinformatics methods. Expression profiling revealed that SmHD-Zip I genes exhibited distinctive tissue-specific patterns and divergent responses to ABA, PEG, and NaCl stresses. SmHD-Zip12 responded the most strongly to ABA, PEG, and NaCl, so it was used for transgenic experiments. The overexpression of SmHD-Zip12 significantly increased the content of cryptotanshinone, dihydrotanshinone I, tanshinone I, and tanshinone IIA by 2.89-fold, 1.85-fold, 2.14-fold, and 8.91-fold compared to the wild type, respectively. Moreover, in the tanshinone biosynthetic pathways, the overexpression of SmHD-Zip12 up-regulated the expression levels of SmAACT , SmDXS , SmIDS , SmGGPPS , SmCPS1 , SmCPS2 , SmCYP76AH1 , SmCYP76AH3 , and SmCYP76AK1 compared with the wild type. Conclusions This study provides information the possible functions of the HD-Zip I family and lays a theoretical foundation for clarifying the functional mechanism of the SmHD-Zip12 gene in regulating the synthesis of tanshinone in S. miltiorrhiza .