Inorganic phosphate (Pi) availability is an important factor that affects the growth and yield of crops, thus an appropriate and effective response to Pi-fluctuation is critical. However, how crops orchestrate Pi-signaling and growth under Pi-starvation conditions to optimize the growth defense tradeoff remains unclear. Here we show that a Pi-starvation induced transcription factor NIGT1 (NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1) controls plant growth and prevents a hyperresponse to Pi-starvation by directly repressing the expression of growth-related and Pi-signaling genes to achieve a balance between growth and response under a varying Pi environment. NIGT1 directly binds to the promoters of Pi-starvation signaling marker genes, like IPS1, miR827 and SPX2, under Pi-deficient conditions to mitigate the Pi-starvation responsive (PSR). It also directly represses the expression of vacuolar Pi efflux transporter genes VPE1/2 to regulate plant Pi-homeostasis. We further demonstrate that NIGT1 constrains shoot growth by repressing the expression of growth-related regulatory genes, including brassinolide signal transduction master regulator BZR1, cell division regulator CYCB1;1, and DNA replication regulator PSF3. Our findings reveal the function of NIGT1 in orchestrating plant growth and Pi-starvation signaling, and also provide evidence that NIGT1 acts as a safeguard to avoid hyperresponse during Pi-starvation stress in rice.
Working model of OsNIGT1 balances the tradeoff between Pi starvation response and growth in rice
The black and gray lines represent the active and inactive processes, respectively. Arrow lines indicate positive effects, and lines ending with a short bar represent negative effects. The different size of protein diagrams represents protein level. PSI in dicates phosphate starvation induced genes. A detailed description of the model can be found in the Discussion section in the paper.
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