The high light-inducible protein (NyHLIP1) has a long half-life and possesses an important role in the high light stress response of resurrection intertidal red algae

The transiently existed high light (HL)-inducible proteins (HLIPs) or one-helix proteins (OHPs) in cyanobacteria and higher plants play essential roles in HL stress response. However, little is known about HLIPs in intertidal algae, which are periodically exposed to direct sunlight. We studied the changes and potential functions of one HLIP protein (NyHLIP1) in the typical resurrection intertidal red alga Neopyropia yezoensis. Although NyHLIP1 was degraded in a low light (LL) culture and induced by HL conditions, NyHLIP1 existed much longer than that in Cyanobacteria and higher plants, which was up to >240 h (10 days) in cultured samples after a 6-h HL induction. Furthermore, the photosynthetic parameter analysis showed that the F-v/F-m (maximum quantum yield of PSII), Y(II) (effective quantum yield of PSII), ETRII (electron transfer rates of PSII) and P700(+) reduction rates were decreased, while Y(NO) (yield of non-regulated energy dissipation of PSII) was increased, in the two NyHLIP1 downregulated mutants (RNAi-type: Ri32; co-suppression-type: CS32) after HL treatment, which were all similar under LL condition. The D1 content in knockdown strains did not degrade after HL treatment compared with a noticeable degradation after 6-h HL treatment in WT. These results indicated that NyHLIP1 might play an important role in the response of photosystem, especially photosystem II, to HL stress in this resurrection intertidal red algae.