B-GATAs Fine Tune Greening

Bastakis et al. investigate control of the greening process in Arabidopsis https://doi.org/10.1105/tpc.17.00947.

By Emmanouil Bastakis

Pale green mutants can partially restore their greening defects, if GNC and GNL proteins are overexpressed.

Background: The greening of the plants is based on the synthesis and accumulation of the chlorophylls, which takes place in chloroplasts. Chlorophylls capture the energy from sunlight and then use it to convert CO2 from the atmosphere into sugars, which are the basic building blocks for plant growth. A lot of research has been focused on the functional and biochemical characterization of enzymes that play important roles in greening, but little is known about the regulation of the underlying genes, which greatly influences this process as well.

Question: We wanted to understand the function of the B-GATA transcription factors GNC and GNL, proteins known to control the expression of genes and to have a role in the greening of Arabidopsis thaliana. To answer this question we combined gene expression studies together with genetic, molecular, metabolic, and physiological experiments.

Findings: We found that GNC and GNL promote greening in Arabidopsis by controlling the expression of genes implicated in five distinct pathways. These include i) regulating genes encoding enzymes in chlorophyll biosynthesis, ii) influencing phytochrome signaling, which plays an important role in the perception of light, iii) regulationg factors known as SIGs that control the expression of genes in the chloroplast genome, iv) influencing signaling between the chloroplast and the nucleus, and v) influencing genes encoding other proteins, such as GLKs, with established roles in the regulation of greening.

Next steps: Our work shows that GNC and GNL are major players in the regulation and the fine tuning of greening. Further understanding of this process is directly relevant to crop performance. Future work includes investigating the relationships of GNC and GNL with other regulators of greening and in their exact role in coordinating signalling between the chloroplast and nucleus.

Emmanouil Bastakis, Boris Hedtke, Carina Klermund, Bernhard Grimm, and Claus Schwechheimer. (2018). Multifaceted role of LLM-domain B-GATA factors in the control of greening in Arabidopsis thaliana. Plant Cell. Published February https://doi.org/10.1105/tpc.17.00947.