Low temperature tolerance in Antarctic microalga, Chaetoceros regracile

Abstract

Antarctic microalga, Chaetoceros regracile was investigated to dissect the mechanism of survival in the low temperature condition. The growth of C. regracile was compared in different culture conditions. C. regracile was actively growing in 4oC culture condition and the growth rate of C. regracile under continuous light was significantly higher than the growth rate under light- dark culture condition. The pool size of the xanthophyll cycle pigment diadinoxanthin (DD) and diatoxanthin (DT) in C. regracile relyed on illumination conditions during culture. On exposure to high-light intensity, extensive de-epoxidation of DD to DT was observed in low temperature condition, which suggested that xanthophyll cycle plays a role in the prevention of photoinhibitory damage to the photosynthetic apparatus. To isolate the low temperature specific genes of Chaetoceros regracile, cDNAs were generated by RT-PCR and they were amplified with arbitrary primers to compare genes that are differentially expressed between 10oC and 4oC culture conditions. PCR based partial cloning of C. regracile genes were sequenced and characterized. Putative function of these genes that were isolated from this investigation will be discussed.