PbNAC3 coordinates AsA generation and ABA biosynthesis to improve salt tolerance in pear

In plants, dehydroascorbate reductase (DHAR) is one of the key enzymes in AsA generation during the AsA-GSH cycle, which helps maintain the normal metabolic level of AsA. However, the molecular mechanism of DHAR's response to salt stress is still unknown. Our experiments show a ping-pong mechanism, in which DHA is combined with free reductase DHAR, and free reductase DHAR is combined with GSH in the form of sulfenylation to promote AsA generation in response to salt stress. This mechanism is inhibited by H₂O₂-mediated sulfenylation modification. The overexpression of PbDHAR3 in pear callus and Arabidopsis plants alleviated salt-induced damage, while its silencing decreased salt tolerance in Pyrus betulaefolia. PbNAC3 can activate the expression of PbDHAR3 by directly binding to the promoter. The overexpression of PbNAC3 in pear callus improved salt tolerance, while silencing it reduced tolerance in P. betulaefolia. Overexpression of PbNAC3 in Arabidopsis plants is able to adjust the trade-off between plant growth and salt stress. Higher expression levels of NCEDs or PYLs, and higher ABA content were observed under salt treatment. Further experiments demonstrate that PbNAC3 activates PbNCED5 through interaction with cis-regulatory elements. Overall, our results show that PbNAC3 plays a critical role in salt stress response by targeting the promoters of PbDHAR3 and PbNCED5, promoting AsA generation and ABA biosynthesis. This study will deepen our understanding of the mechanisms underlying the trade-offs between plant growth and stress tolerance and assist the development of stress-resistant, high-yield crops.