Identification and expression analysis of the gene lhcSR associated with adaptation to light and low temperature stress in the green tide forming alga Ulva prolifera

As the dominant species of the green tide-forming algae in the Yellow Sea of China during the past four years, Ulva prolifera was proposed as having evolved a perfect response mechanism to deal with different light and temperature stress. The LHCSR (also known as LI818 in green algae and LHCX in diatoms) protein is a stress-related member of the LHC family found only in algae. The homologues in the green alga Chlamydomonas were up-regulated in response to a variety of stresses and required for energy quenching. In this study, we cloned a putative lhcSR full-length cDNA sequence from U. prolifera and analysed the expression in response to various temperature and illumination gradients. The results showed that expression of lhcSR was up-regulated by light and transiently accumulated in 1 h. Expression of lhcSR could also be induced by low-temperature stress and could sustain the up-regulation for up to 6 days. These data suggest that the lhcSR gene in U. prolifera is involved in the adaption to the light and low-temperature stress in both the short and long term.