Characterization of three members of the multigene family coding for isoforms of the chlorophyll a/b binding protein Lhcb1 in spinach

Multiple Lhcb1 and Lhcb2 isoforms have been identified in plants, whose precise functions have yet to be understood. In spinach, a proteomic analysis of major antenna proteins revealed three homologous short polypeptides, corresponding to putative distinct Lhcb1 isoforms with different phosphorylation sites. In this paper we report the identification of the complete coding sequences for the three spinach Lhcb1 isoforms. 3’ RACE analysis identifies several transcripts for each single coding region, allowing us to hypothesize the presence in the spinach genome of multiple gene copies, with different 3’-UTR. In leaves, under normal light conditions, about the same relative amounts of the three transcripts are present. However, Real-Time PCR analysis shows that under long term white light exposure, a differential transcript accumulation occurs. The occurrence of three genes encoding Lhcb1 isoforms supports the hypothesis of a complex organization of spinach LHCII, and a possible specific role for the different isoforms in plant adaptation to different light conditions. Furthermore, the identification of multiple transcripts suggests that the expression of the three coding sequences may