LLM-Domain B-GATA Transcription Factors Play Multifaceted Roles in Controlling Greening in Arabidopsis.

Chlorophyll accumulation and chloroplast development are regulated at multiple levels during plant development. The paralogous LLM-domain B-GATA transcription factors GNC and GNL contribute to chlorophyll biosynthesis and chloroplast formation in light-grown seedlings. Whereas there is already ample knowledge about the transcriptional regulation of and , the identity of their downstream targets is largely unclear. Here, we identified genes controlling greening directly downstream of the GATAs by integrating data from RNA-sequencing and microarray data sets. We found that genes encoding subunits of the Mg-chelatase complex and 3,8-divinyl protochlorophyllide a 8-vinyl reductase (DVR) likely function directly downstream of the GATAs and that expression is limiting in the pale-green mutants. The GATAs also regulate the nucleus-encoded () factor genes, which control transcription in the chloroplast and suppress the greening defects of mutants. Furthermore, and act, at the gene expression level, in an additive manner with the () and transcription factor genes, which are also important for proper chlorophyll accumulation. We thus reveal that chlorophyll biosynthesis genes are directly controlled by LLM-domain B-GATAs and demonstrate that these transcription factors play an indirect role in the control of greening through regulating factor genes.