AUTHOR=Liang Guoping , Li Yanmei , Wang Ping , Jiao Shuzhen , Wang Han , Mao Juan , Chen Baihong 

TITLE=VaAPL1 Promotes Starch Synthesis to Constantly Contribute to Soluble Sugar Accumulation, Improving Low Temperature Tolerance in Arabidopsis and Tomato

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.920424

DOI=10.3389/fpls.2022.920424

ISSN=1664-462X

ABSTRACT=<p>ADP-glucose pyrophosphorylase (AGPase) is a key rate-limiting enzyme involved in starch synthesis. APL1, an AGPase large subunit, plays an important role in the growth and development of grapes; however, its function in withstanding low temperature (LT) remains elusive. Hence, <italic>VaAPL1</italic> was cloned from <italic>Vitis amurensis</italic> (Zuoshan I), and its function was characterized. The gene was highly expressed in the phloem of <italic>V. amurensis</italic> during winter dormancy (0, −5, and − 10°C). Phylogenetic relationships demonstrated that VaAPL1 was closely genetic related to SlAPL1 (from <italic>Solanum lycopersicum</italic>), and clustered into I group. Further, <italic>VaAPL1</italic> was ectopically expressed in <italic>Arabidopsis thaliana</italic> (ecotype Columbia, Col) and tomato (“Micro-Tom” tomato) to characterize its function under LT. Compared with Col, the average survival rate of <italic>VaAPL1</italic>-overexpressing <italic>A. thaliana</italic> exceeded 75.47% after freezing treatment. Moreover, reactive oxygen species (ROS) content decreased in <italic>VaAPL1</italic>-overexpressing <italic>A. thaliana</italic> and tomato plants under LT stress. The activities of AGPase, and starch contents in <italic>VaAPL1</italic>-overexpressing <italic>A. thaliana</italic> were higher than in Col after LT stress. The contents of sucrose and glucose were accumulated in overexpressing plants compared with wild-type at 0 h and 24 h after LT stress. Transcriptome sequencing of overexpressing tomato plants revealed involvement in sugar metabolism and the hormone signal pathway, and Ca<sup>2+</sup> signaling pathway-related genes were up-regulated. Hence, these results suggest that overexpression of <italic>VaAPL1</italic> not only ensured sufficient starch converting into soluble sugars to maintain cell osmotic potential and provided energy, but also indirectly activated signal pathways involved in LT to enhance plant tolerance.</p>