Overexpression of the First Peanut-Susceptible Gene, <i>AhS5H1</i> or <i>AhS5H2</i>, Enhanced Susceptibility to <i>Pst</i> DC3000 in Arabidopsis
2023
Bingbing Liang | Yuanjun Bai | Chaoqun Zang | Xue Pei | Jinhui Xie | Ying Lin | Xiaozhou Liu | Taswar Ahsan | Chunhao Liang
Salicylic acid (SA) serves as a pivotal plant hormone involved in regulating plant defense mechanisms against biotic stresses, but the extent of its biological significance in relation to peanut resistance is currently lacking. This study elucidated the involvement of salicylic acid (SA) in conferring broad-spectrum disease resistance in peanuts through the experimental approach of inoculating SA-treated leaves. In several other plants, the salicylate hydroxylase genes are the typical susceptible genes (<i>S</i> genes). Here, we characterized two SA hydroxylase genes (<i>AhS5H1</i> and <i>AhS5H2</i>) as the first <i>S</i> genes in peanut. Recombinant AhS5H proteins catalyzed SA in vitro, and showed SA 5-ydroxylase (S5H) activity. Overexpression of <i>AhS5H1</i> or <i>AhS5H2</i> decreased SA content and increased 2,5-DHBA levels in Arabidopsis, suggesting that both enzymes had a similar role in planta. Moreover, overexpression of each <i>AhS5H</i> gene increased susceptibility to <i>Pst</i> DC3000. Analysis of the transcript levels of defense-related genes indicated that the expression of <i>AhS5H</i> genes, <i>AhNPR1</i> and <i>AhPR10</i> was simultaneously induced by chitin. Overexpression of each <i>AhS5H</i> in Arabidopsis abolished the induction of <i>AtPR1</i> or <i>AtPR2</i> upon chitin treatment. Eventually, <i>AhS5H2</i> expression levels were highly correlated with SA content in different tissues of peanut. Hence, the expression of <i>AhS5H1</i> and <i>AhS5H2</i> was tissue-specific.
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