Early dynamics of photosynthetic Lhcf2 and Lhcf15 transcription and mRNA stabilities in response to herbivory-related decadienal in Phaeodactylum tricornutum

Abiotic and biotic stresses widely reduce light harvesting complex (LHC) gene expression in higher plants and algae. However, control mechanisms and functions of these changes are not well understood. During herbivory, marine diatom species release oxylipins that impair grazer reproduction and serve as signaling molecules to nearby undamaged diatoms. To examine LHC mRNA regulation by oxylipin exposure, the diatom Phaeodactylum tricornutum was treated with a sublethal concentration of trans,trans-2,4-decadienal (DD) during the light cycle. Transcriptome analyses revealed extensive suppression of LHC mRNAs and a smaller set of up-regulated LHC mRNAs at 3 h. For two divergently regulated LHCF antennae family mRNAs, in vivo 4-thiouracil metabolic labeling was used to distinguish synthesis and degradation rates. Within 3 h of DD exposure, Lhcf2 mRNA levels and transcription were strongly suppressed and its mRNA half-life decreased. In contrast, Lhcf15 mRNA mainly accumulated between 3–9 h, its transcription increased and its mRNA was highly stabilized. Hence, DD-treated cells utilized transcriptional and mRNA stability control mechanisms which were likely major factors in the differing Lhcf2 and Lhcf15 expression patterns. Widespread LHC mRNA regulation and possible effects on photosynthesis may contribute to enhanced fitness in cells impacted by herbivory and other stresses.