Coding-sequence confirmation of rice OsLHTs with their differential expressions involved in N-nutritional status, tissue specificity and grain production

Despite the biological importance of amino acid movement into/within the plant, LHT-type amino acid transporters are limitedly studied in crops. In this short communication, by sequence analysis in silico, reverse-transcription PCR and DNA-sequencing we have provided experimental evidence for the actual expression of full-length coding sequences of six OsLHTs in rice. Furthermore, transcriptional regulation assays indicated that OsLHT1–6 in roots and OsLHT1/6 in shoots positively responded to N-starvation at a vegetative stage, and that OsLHT1/3/4 were expressed at relatively high levels in both aged- and flag-leaves but OsLHT5 mRNA occurred mostly in the old leaves, proposing their putative functions in amino acid transport from such source tissues. Notably, a transgenic approach using senescence-inducible promoter allowed to demonstrate that an overexpression of OsLHT5 in the aged rice leaves could remarkably enhance internal nitrogen translocation to growing or functional flag leaves, increase respectively grain yield and total free amin-acid content by approximately 10% and 25%, providing an interesting genetic target for molecular-breeding aiming at improving N-use-efficiency and productivity. Taken together, our current work is believed to favour an intensive investigation of molecular and physiological functions of OsLHTs in rice amino acid transport processes in the future.