Internal phosphate starvation signaling and external phosphate availability have no obvious effect on the accumulation of cadmium in rice

Phosphorus(P)is a limiting nutrient element for crop.To obtain maximum crop yield,P fertilizer is often over-applied,which leads to accelerating exhaustion of phosphate resources and serious environmental problems.Reducing the application of P fertilizer and enhancing the P utilization efficiency of crops are significant for the sustainable development of agriculture.Cadmium(Cd)contamination in rice is another serious agricultural issue.However,whether reducing the application of P fertilizer and enhancing the P utilization efficiency of crops will increase the risk of Cd accumulation in crops remains obscure.In this study,we are aiming to elucidate the relationship between Cd and P in rice from physiological and genetic perspectives.For this purpose,the wild type(WT)rice plants and phosphate(Pi)-starvation signaling repressed mutant phr2 were used to analyze the relationship between Cd and P.Here,we found that Cd stress could promote P accumulation and induce Pi-starvation signaling in WT and phr2 shoots under Pi-sufficient condition in a PHOSPHATE STARVATION RESPONSE 2(PHR2)independent manner.Besides,the expression level of Cd transporter of OsNramp5 and the uptake speed of Cd2+were not obviously changed under Pi-sufficient and Pi-deficient conditions.Furthermore,our Cd determination results showed that the Cd concentrations in WT and phr2 were not obviously changed under Pi-sufficient and Pi-deficient conditions.These results indicate that the external P availability and internal Pi-starvation signaling cannot obviously affect the accumulation of Cd in rice seedling.

NIGT1 represses plant growth and mitigates phosphate starvation signaling to balance the growth response tradeoff in rice

Inorganic phosphate(Pi)availability is an important factor which 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 starvationinduced transcription factor NIGT1(NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1)controls plant growth and prevents a hyper-response to Pi starvation by directly repressing the expression of growth-related and Pisignaling 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,mi R827,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 hyper-response during Pi starvation stress in rice.