Light induces peroxisome proliferation in Arabidopsis seedlings through the photoreceptor phytochrome A, the transcription factor HY5 HOMOLOG, and the peroxisomal protein PEROXIN11b

Mintu Desai and Jianping Hu ^*

Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824

^* Corresponding author; email: huji{at}msu.edu.

Peroxisomes are single membrane-delimited subcellular organellesthat carry out numerous vital metabolic reactions in nearlyall eukaryotes. Peroxisomes alter their morphology, abundance,and enzymatic constituents in response to environmental cues,yet little is known about the underlying mechanisms. In thiswork, we investigated the regulatory role of light in peroxisomeproliferation in Arabidopsis thaliana. We provide evidence thatlight induces proliferation of peroxisomes in Arabidopsis seedlingsand that the peroxisomal protein PEX11b plays an important rolein mediating this process. The far-red light receptor phyA andthe bZIP transcription factor HYH are both required for theup-regulation of PEX11b in the light. We further demonstratethat the phyA and hyh mutants exhibit reduced peroxisome abundance,a phenotype that can be rescued by overexpressing PEX11b inthese plants. The HYH protein is able to bind to the promoterof PEX11b, suggesting that the PEX11b gene is a direct targetof HYH. We conclude that HYH and PEX11b constitute a novel branchof the phyA-mediated light signaling cascade, which promotesperoxisome proliferation during seedling photomorphogenesis.