CHLOROPLAST RETROGRADE SIGNALLING INVOLVED IN ALTERNATIVE SPLICING REGULATION

EZEQUIEL PETRILLO; MICAELA AMALIA GODOY HERZ; ALBERTO RODOLFO KORNBLIHTT

Campana, Buenos Aires, Argentina

Congreso; Biology in Balance; 2009

Whereas the fraction of genes with alternative splicing isnearly 70% in humans it is only 30% in Arabidopsis. Similarly, much more is known about alternative splicingregulation in mammalian cells compared to plants.With the aim of understanding the mechanisms that regulatealternative splicing in plants, we studied the RUBISCO Activase and the RSp31 SR protein genes, whose alternativesplicing patterns vary depending on light conditions. In both genes, light exposure causes an increase in theproportion of the shorter mRNA isoforms. We found that light intensity, but not its quality, seems to be the factorthat elicits changes in splicing patterns. This is evidenced by realizing that blue or red light produce similar effectsas white light and that different photoreceptor mutant plants behave as the WT in the alternative splicing responseto white light. Consistently, drugs that inhibit the electronic photosynthetic transport abolish the effects of light onalternative splicing. The involvement of a chloroplast signal was explored by using chloroplast signaling mutants.Furthermore, H2O2 treatment of seedlings in the dark duplicates the effects of light on alternative splicing, whichsuggests that peroxides (or ROS) might act as signal intermediates. A correlation between the proportions of splicingisoforms with gene expression suggests a transcriptional regulation of alternative splicing. By using splicing reporterminigenes in BY-2 cells, we are investigating a possible coupling to transcription in plants.