Characterization and functional insights of photosynthetic genes MnPsbA, MnRbcL, and MnRCA in mulberry

Photosynthesis is the basic metabolic process of plants and the efficiency of photosynthesis is a direct result of crop yield and quality. The functions of MnPsbA, MnRbcL, and MnRCA in mulberry were investigated. The coding regions of MnPsbA, MnRbcL, and MnRCA were found to be 1062 bp, 1428 bp, and 1314 bp in length, respectively, encoding proteins of 353, 475, and 437 amino acids. MnPsbA, AtPsbA, PtPsbA1, and PtPsbA2 all contain the highly conserved Photo_RC domain and exhibit high sequence similarity. Both MnRbcL and AtRbcL contain the RuBisCO_large and RuBisCO_large_N domains, showing high homology, while PtRbcL lacks the RuBisCO_large_N domain at its C-terminus. MnRCA shares 80.7% homology with AtRCA, which 83.4% and 83.0% homology with PtRCA1 and PtRCA2, respectively. All these proteins contain the highly conserved AAA domain. The tertiary structures of MnPsbA, MnRbcL, and MnRCA show significant differences in folding and spatial orientation. Expression levels of MnPsbA, MnRbcL, and MnRCA were highest in E1 and lowest in H32. Transgenic Arabidopsis leaves exhibited significantly higher Pn peak values compared to the wild type. Additionally, the transgenic lines had significantly higher ΦPSII, qP, Chla, Chlb, and total Chl levels than the wild type. Although RuBP enzyme activity was greater in the transgenic lines, the increase was not significant. These results indicate that MnPsbA, MnRbcL, and MnRCA contribute to the photosynthesis of mulberry to varying extents. Enhancing the photosynthetic rate of mulberry leaves through these genes could potentially increase yield.