AUTHOR=Xue Jinyu , Zeng Pingsheng , Cui Jiebing , Zhang Yingting , Yang Junjie , Zhu Lijuan , Hu Hailiang , Xu Jin 

TITLE=Physiological and gene expression changes of Cryptomeria fortunei Hooibrenk families under heat stress

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1083847

DOI=10.3389/fpls.2023.1083847

ISSN=1664-462X

ABSTRACT=<p>Heat stress is one of the major abiotic stresses affecting plant growth and productivity. <italic>Cryptomeria fortunei</italic> (Chinese cedar) is an excellent timber and landscaping tree species in southern China thanks to its beautiful appearance, straight texture and ability to purify the air and improve the environment. In this study, we first screened 8 excellent <italic>C. fortunei</italic> families (#12, #21, #37, #38, #45, #46, #48, #54) in a second generation seed orchard. We then analyzed the electrolyte leakage (EL) and lethal temperature at 50% (LT<sub>50</sub>) values under heat stress, to identify the families with the best heat resistance (#48) and the lowest heat resistance (#45) and determine the physiological and morphological response of different threshold-resistance of <italic>C</italic>. <italic>fortune</italic> to heat stress. The relative conductivity of the <italic>C. fortunei</italic> families showed an increasing trend with increasing temperature, following an “S” curve, and the half-lethal temperature ranges between 39°C and 43.2°C. The activities of SOD and POD fluctuated in the early stage of stress but decreased after 37°C. We observed the changes in the cell ultrastructure at 43°C, and the mesophyll cell structure of #48 was less damaged than that of #45. Eight heat resistance gene, including <italic>CfAPX1</italic>, <italic>CfAPX2</italic>, <italic>CfHSP11</italic>, <italic>CfHSP21</italic>, <italic>CfHSP70</italic>, <italic>CfHSFA1a</italic>, <italic>CfHSFB2a</italic> and <italic>CfHSFB4</italic>, were all up-regulated in #45 and #48, and there were significant differences between #45 and #48 under different heat stress treatments. We found a significant difference in heat tolerance between #45 and #48, such that #48 shows higher heat tolerance capability and could be exploited in breeding programs. We conclude that the strongly heat-resistant family had a more stable physiological state and a wider range of heat stress adaptations.</p>