Expression and functional analysis of the PmPsbS gene reveals its role in the regulatory mechanism of non-photochemical quenching(NPQ)in heteroblastic foliage of Pinus massoniana seedlings

To prevent severe oxidation damage to photosystems,excess absorbed light energy is dissipated as heatth rough a process known as non-photochemical quenching(NPQ).Heteroblastic foliage is observed during the first growth season of Pinus massoniana,giving rise to primary needle seedling(PNS)and secondary needle seedling(SNS).Notably,there are distinct differences in NPQ between PNS and SNS.However,the molecular regulatory mechanism of NPQ in the heteroblastic foliage of P.massoniana remains unclear.Here,PmPsbS was investigated and functionally analysed.The PmPsbS protein contains two conserved domains and four transmembrane regions and is primarily located in the thylakoid membrane of chloroplasts.The core region of the PmPsbS promoter is located between-852 and-330 bp,including predicted binding sites for light-responsive elements,G-box elements,and MYB transcription factors.Moreover,we predicted that P.massoniana would contain light-responsive MYB gene family members,encoding proteins that may bind to specific sites within the PmPsbS gene promoter to regulate its expression.Different photoprotective and light energy partitioning mechanisms in response to seasonal variation in the primary and secondary needles.However,under shade stress conditions alone,SNS was more susceptible to light inhibition,and the expression mechanism of PmPsbS differed between P.massoniana seedlings with heteroblastic foliage.These results indicated that PmPsbS can circumvent photoinhibition and enhance photoprotection,and plays an important role in the adaptation of the heteroblastic foliage of P.massoniana to light environments.