OsARF16-mediated Auxin Signaling Participates In Phosphorus Starvation Response In Rice (Oryza Sativa L.)

In dicotyledonous model plant Arabidopisis thaliaiia, the cross-talk between auxin and phosphorus signal was high-profile; in monocotyledon model plant rice, auxin signal transduction and phosphorus absorption metabolism has been researched well, but the both relationship retain unclear. In order to understand interaction between auxin and phosphorus signal in detail, and exploring new ways of efficient utilization of phosphorus in rice; we analyzed the knockout mutant and over-expression materials of auxin response factor OsARF16, finding that the mutant osarfl6lost functions of response to auxin and phosphorus deficiency. The results indicated that OsARFl6is a key gene for linkage of the both signals.OsARF16is an auxin response active factor, which consists of a typical DBD, CTD, and MR rich in glutamine. The knockout of OsARF16caused auxin insensitive phenotype, and then severely impaired the response to exogenous hormones in PR, LR, RH and AR. OsARF16presented a constitutive expression pattern in all tissues, especially highly expressed in root and vascular tissue by OsARF16promoter::GUS staining. And, the expression pattern was regulated by auxin and polar auxin transport inhibitor. The IAA content in osarf16mutant was higher than in NIP, but lower than in NIP under exogenous hormone treatment. As the result of qRT-PCR shown, most of auxin transporter encoding genes OsPINs, OsLAXs and OsPGPs in NIP were mightily upregualted by auxin while in osarf16did not. The knockout of OsARF16impacts the expression of auxin transporter genes, slow down polar auxin transporting and lead insensitive to auxin.Phosphorus is one of the essential micronutrient for plant growth and development. At CK condition, more phosphorus accumulated in osarfl6to NIP which was similar to that applied exogenous hormone into NIP, implying that the higher concentration in osarf16might improve phosphate uptake in rice. Phosphorus starvation in NIP trigs root growth, reduces shoot biomass and facilitates iron acquisition; osarfl6lost response to phosphorus starvation and destroyed homoeostasis between iron and phosphate, such as, root-to-shoot was not increased and the iron content was not raised. OsARF16gene was markedly induced by phosphorus starvation in root hair and lateral root; whereas in osarfl6mutant root hair and lateral root development were not obviously improved. These evidences indicated that the phenotype changing by phosphate deficiency was dependent on present of OsARF16. Moreover, six Phosphate Starvation Induced genes (PST) were no longer induced by phosphorus deficiency, and the transduction of phosphate signaling was weakened seriously in osarfl6, which resulted osarf16mutant was insensitive to phosphorus starvation.In conclusion, our research first elucidated that OsARF16plays an important regulation role at response to auxin and phosphorus starvation in rice; provided novel molecular biology and physiology evidences for interaction between auxin and phosphorus starvation response; established the theory foundation for uncovering the co-regualtion mechanism of the two signals.In addition, the biological function of OsARF16was also studied in sugar absorption and metabolism:The knockout of OsARF16altered the sugar balance in rice, and reduced the suppression of plant growth by high concentration of sugar. We also developed OsIAA8promoter::GUS and OsIAA8over-expression transgenic materials of auxin early response gene OsIAA8which interacts with OsARF16. This research will promote the perfection of regulation network of auxin and phosphorus starvation response with a core OsARF16. OsARF16as a core in...