AUTHOR=Wang Huiping , Liu Zeci , Xie Jianming , Li Jing , Zhang Jing , Yu Jihua , Hu Linli , Zhang Guobin 

TITLE=The CaALAD Gene From Pepper (Capsicum annuum L.) Confers Chilling Stress Tolerance in Transgenic Arabidopsis Plants

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.884990

DOI=10.3389/fpls.2022.884990

ISSN=1664-462X

ABSTRACT=<p>The <italic>ALAD</italic> gene encodes an enzyme that is essential for chlorophyll biosynthesis and is involved in many other physiological processes in plants. In this study, the <italic>CaALAD</italic> gene was cloned from pepper and sequenced. Multiple sequence alignment and phylogenetic analysis of ALAD proteins from nine plant species showed that <italic>ALAD</italic> is highly conserved, and that CaALAD shows the highest homology with the ALAD protein from eggplant. Subcellular localization indicated that the CaALAD protein is mainly localized to the chloroplasts. After transferring <italic>CaALAD</italic> into the <italic>Arabidopsis thaliana</italic> genome, cold tolerance of the transgenic lines improved. Overexpression of <italic>CaALAD</italic> increased the relative transcription of the <italic>AtCBF2</italic>, <italic>AtICE1</italic>, and <italic>AtCOR15b</italic> genes in transgenic <italic>Arabidopsis</italic> plants exposed to low temperature (4°C) stress, and the contents of reactive oxygen species decreased due to increased activities of superoxide dismutase, peroxidase, and catalase. Moreover, chlorophyll biosynthesis, as determined by the contents of porphobilinogen, protoporphyrin IX, Mg-protoporphyrin IX, prochlorophyllate, and chlorophyll in the transgenic <italic>Arabidopsis</italic> plants, increased in response to low temperature stress. In addition, the transgenic lines were more sensitive to exogenous ALA and NaHS, and the H<sub>2</sub>S content of transgenic line plants increased more rapidly than in the wild-type, suggesting that <italic>CaALAD</italic> may respond to low temperatures by influencing the content of H<sub>2</sub>S, a signaling molecule. Our study gives a preliminary indication of the function of <italic>CaALAD</italic> and will provide a theoretical basis for future molecular breeding of cold tolerance in pepper.</p>