Photoprotection of antartic microalga, Chaetoceros neogracile

Abstract

Antarctic diatom, Chaetoceros neogracile had survival mechanism in near or below freezing tempterature of culture condition. C. neogracile was actively growing in 4oC culture condition and the growth rate of C. neogracile 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. neogracile 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 neogracile, 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. neogracile genes were sequenced and characterized. 19 clones were obtained, and based on a Blast search, 6 genes were selected. To see how these genes are expressed in 4 oC and 10 oC conditions, RNA expression was carried out. Results will be discussed in detail. This work was supported by KOSEF grant.