Cloning and Expression Activity Analysis of Rubisco Small Subunit Gene Promoter in Populus × xiaohei

Ribulose-1,5-diphosphate carboxylase/oxygenase（Rubisco） is a key enzyme in photosynthesis, in which small subunits（rbcS） are encoded by nuclear genes and mainly expressed in leaves. In this study, the Rubisco small subunit genes PxrbcS1 and PxrbcS2, which are highly expressed in Populus × xiaohei’s leaves, were determined by RT-qPCR technology, and their upstream promoters of 2 240 and 2 174 bp were cloned respectively. The results of promoter element analysis showed that the promoters of PxrbcS1 and PxrbcS2 had multiple elements related to light induced expression, including G-box, MRE and Box4 elements. Plant expression vectors of pBI-121-p PxrbcS1::GUS and pBI-121-p PxrbcS2::GUS were constructed and genetically transformed into 84K poplar（P. alba×P. glandulosa）. GUS histochemical staining and qPCR expression analysis showed that the promoters of PxrbcS1 and PxrbcS2 could drive the GUS gene to express in 84K poplar leaves with high specificity. In conclusion, the above results showed that PxrbcS1 and PxrbcS2 promoters with high leaf expression activity were successfully cloned from P.×xiaohei, and the promoters might be applied to the study of gene functions related to plant photosynthesis and genetic operations to improve photosynthesis in plants, including poplars.