Abstract:In order to understand the function of POR gene in Cymbidium sinense ‘Dharma’, one POR gene family member CsPORB was cloned from young leaves. The CsPORB gene contained an open reading frame of 1 200 bp, which encoded a protein of 399 amino acids with molecular weight of 43.13 kDa and theoretical isoelectric point of 9.30. Sequence alignment showed that CsPORB was highly homologous to the sequence of POR family protein of other species, indicating conservative evolution of this gene family. The CsPORB expression showed obviously difference in different developmental stages and tissues, and high expression in growing young leaves. Furthermore, both of the PORB and its downstream chlorophyll biosynthesis enzyme activity increased in transgenic 35S:CsPORB Arabidopsis, as well as chlorophyll content, especially 35S:CsPORB transgenic plants remained green under dark for one week. Therefore, CsPORB could play an important roles in chlorophyll synthesis pathway of Cymbidium sinense ‘Dharma’.