Shaikhali J, Barajas-Lopéz J, Ötvös K, Kremnev D, Sánchez Garcia A, Srivastava V, Wingsle G, Bako L, Strand Å
The CRYPTOCHROME1-dependent response to excess light is mediated through the transcriptional activators ZINC FINGER PROTEIN EXPRESSED IN INFLORESCENCE MERISTEM LIKE1 and 2 in Arabidopsis
Plant Cell, 2012, 24(7):3009-25


Abstract
Exposure of plants to light intensities that exceed the electron utilization capacity of the chloroplast has a dramatic impact on nuclear gene expression. The photoreceptor Cryptochrome 1 (cry1) is essential to the induction of genes encoding photoprotective components in Arabidopsis thaliana. Bioinformatic analysis of the cry1 regulon revealed the putative cis-element CryR1 (GnTCKAG) and here we demonstrate an interaction between CryR1 and the zinc finger GATA type transcription factors ZINC FINGER PROTEIN EXPRESSED IN INFLORESCENCE MERISTEM LIKE1 and 2 (ZML1/2). The ZML proteins specifically bind to the CryR1 cis-element as demonstrated in vitro and in vivo and TCTAG was shown to constitute the core sequence required for ZML2 binding. In addition, ZML2 activated transcription of the YFP reporter gene driven by the CryR1 cis-element in Arabidopsis leaf protoplasts. T-DNA insertion lines for ZML2 and its homologue ZML1 demonstrated mis-regulation of several cry1-dependent genes in response to excess light. Furthermore, the zml1 and zml2 T-DNA insertion lines displayed a high irradiance-sensitive phenotype with significant photoinactivation of PSII, indicated by reduced Fv/Fm, and severe photobleaching. Thus, we have identified the ZML2 and ZML1 GATA transcription factors as two essential components of the cry1-mediated photoprotective response.

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