Transgenic Rice Overexperessing a Tomato Mitochondrial Phosphate Transporter, SlMPT3;1, Promotes Phosphate Uptake and Increases Grain Yield

Mitochondrial phosphate transporter plays an important regulatory role in promoting the uptake and transport of phosphate in plants. In this study, the SlMPT3;1 gene, a member of mitochondrial phosphate transporter family in tomato, was isolated and transformed into the rice Oryza sativa L.ssp. japonica cultivar Kitaake. The SlMPT3;1 is localized to the mitochondrial membrane and functions in compensating the phosphate uptake in yeast MB192 mutant that is defective in phosphate transport under Pi deficiency. RT-qPCR showed that the SlMPT3;1 is expressed in all of tomato tissues, but highly accumulated in the young leaves and stems under Pi deficiency. The data demonstrated that at least two copies of the SlMPT3;1 gene are inserted into the rice genome, and the transcripts of the SlMPT3;1 mRNA are highly accumulated in the roots of the transgenic rice. The overexpression of the SlMPT3;1 gene not only promotes phosphate uptake by the roots, but also increases the translocation of phosphate from the roots to the shoots in the transgenic rice. The transgenic rice accumulated more chlorophyll and soluble sugar in the shoots than the wild type under Pi deficiency. Microassay sequencing showed that the differentially expressed genes in the transgenic rice are mainly involved in the regulations of biological process and molecular function under Pi deficiency. Further RTqPCR analyses revealed that the differentially expressed genes, which are involved in the regulations of the biological process, cell component, and molecular function, are upregulated under Pi deficiency, and exhibit similar expression trends to the relative expression folds of these partial differentially expressed genes in the transcriptomic analyses. This study suggests that the overexpression of the SlMPT3;1 gene promoted the uptake and transport of phosphate in rice, thus leading to an enhanced increase in tiller number and effective panicle of per plant, and increasing grain yield under Pi deficiency.