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bioRxiv · 10.1101/2021.02.11.430802

Interdependent Iron and Phosphorus Availability Controls Photosynthesis Through Retrograde Signaling

Nam, H.-I.·Shahzad, Z.·Dorone, Y.·Clowez, S.·Zhao, K.·Bouain, N.·Cho, H.·Rhee, S. Y.·Rouached, H.
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Abstract

Iron deficiency hampers photosynthesis and is associated with chlorosis. We recently showed that iron deficiency-induced chlorosis depends on phosphorus availability. How plants integrate these cues to control chlorophyll accumulation is unknown. Here, we show that iron limitation downregulates photosynthesis genes in a phosphorus-dependent manner. Using transcriptomics and genome-wide association analysis, we identify two genes, a chloroplastic ascorbate transporter (PHT4;4) and a nuclear transcription factor (bZIP58), which prevent the downregulation of photosynthesis genes leading to the stay-green phenotype under iron-phosphorus deficiency. Joint limitation of these nutrients induces ascorbate accumulation by activating expression of an ascorbate biosynthesis gene, VTC4, which requires bZIP58. Exogenous ascorbate prevents iron deficiency-induced chlorosis in vtc4 mutants, but not in bzip58 or pht4;4. Our study demonstrates chloroplastic ascorbate transport is essential for preventing the downregulation of photosynthesis genes under iron-phosphorus combined deficiency. These findings uncover a molecular pathway coordinating chloroplast-nucleus communication to adapt photosynthesis to nutrient availability.

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Nam, H.-I., Shahzad, Z., Dorone, Y., Clowez, S., Zhao, K., Bouain, N., Cho, H., Rhee, S. Y., Rouached, H.. 2021-02-12. Interdependent Iron and Phosphorus Availability Controls Photosynthesis Through Retrograde Signaling. https://doi.org/10.1101/2021.02.11.430802

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