SPX4 interacts with both PHR1 and PAP1 to regulate critical steps in phosphorus‐status‐dependent anthocyanin biosynthesis

Abstract

Summary Phosphate (Pi) is the plant‐accessible form of phosphorus, and its insufficiency limits plant growth. The over‐accumulation of anthocyanins in plants is often an indication of Pi starvation. However, whether the two pathways are directly linked and which components are involved in this process await identification. Here, we demonstrate that SPX4, a conserved regulator of the Pi response, transduces the Pi starvation signal to anthocyanin biosynthesis in Arabidopsis. When phr1spx4 plants were grown under low Pi conditions, DFR expression and anthocyanin biosynthesis were induced, which distinguished the plant from the behavior reported in the phr1 mutant. We also provide evidence that SPX4 interacts with PAP1, an MYB transcription factor that controls the anthocyanin biosynthetic pathway, in an inositol polyphosphate‐dependent manner. Through a physical interaction, SPX4 prevented PAP1 from binding to its target gene promoter; by contrast, during Pi‐deficient conditions, in the absence of inositol polyphosphates, PAP1 was released from SPX to activate anthocyanin biosynthesis. Our results reveal a direct link between Pi deficiency and flavonoid metabolism. This new regulatory module, at least partially independent from PHR1, may contribute to developing a strategy for plants to adapt to Pi starvation.

Shifts in the rhizobiome during consecutive in planta enrichment for phosphate‐solubilizing bacteria differentially affect maize P status

“…He et al. (2021) demonstrated that an inhibitor of the phosphate starvation response (SPX4) interacted with PAP1 (production of anthocyanin pigments) under P‐sufficient conditions, while loss of this protein interaction under P‐starvation resulted in induction of anthocyanin biosynthesis genes which proves the link between anthocyanin accumulation and P‐starvation. This anthocyanin production is linked to the light energy captured during photosynthesis.…”

New insights into the evolution of SPX gene family from algae to legumes; a focus on soybean

“…During P deficiency they are rapidly degraded, releasing thus the PHR factors to induce transcription of PSI genes. The two proteins however, also differ, as while OsSPX4 integrates nitrate and phosphate signaling, AtSPX4 does not seem to have this function, but on the other hand integrates phosphate signaling and anthocyanin biosynthesis [11, 55].…”

Corrigendum

“…Since its publication, the authors of He et al . (2021) have brought to our attention an error in their article. The data in Fig.…”