3rd Global Summit on Plant Science
Seoul National University, South Korea
Title: Analysis of OsmiR399 expression and down-regulation of LTN1 in rice
Biography: Minkyun Kim
Among the many miRNAs involved in plant stress responses, miR399 is well known to be involved in controlling phosphate homeostasis by down-regulating the expression of PHO2, which encodes the ubiquitin-conjugating E2 enzyme, UBC24, in Arabidopsis. In this study, to understand the expression of the rice OsmiR399 genes under abiotic stress conditions, the expression of the eleven OsmiR399 (a-k) genes was studied by analyzing the levels of their precursor transcripts (pre-miRNAs) in the roots and shoots of rice seedlings subjected to the stress-responsive phytohormone abscisic acid (ABA). We found that the OsmiR399 genes showed different patterns in pre-miRNA accumulation. In particular, OsmiR399b, OsmiR399d, OsmiR399e, and OsmiR399f showed high and steady accumulation in both the roots and shoots regardless of ABA treatments. However, OsmiR399c and OsmiR399k showed ABA-induced expression in the whole plant body or aerial part of the rice seedlings. In addition, to test the possibility that the putative rice PHO2 ortholog of Arabidopsis, also known as LEAF TIP NECROSIS 1 (LTN1), might be down-regulated by the multiple OsmiR399s with certain sequence divergences, four different lines of transgenic rice plants that overexpress either the constitutively expressed OsmiR399s (OsmiR399d and OsmiR399f) or the ABA-inducible OsmiR399s (OsmiR399c and OsmiR399k) were produced and the levels of OsmiR399 pre-miRNAs and LTN1 transcripts were analyzed. A significant decrease in the accumulation of LTN1 transcripts and an increase in the OsmiR399 pre-miRNAs levels were found in all of the transgenic plants. Based on these results, we concluded that LTN1 is down-regulated by multiple OsmiR399 genes in rice.