Identification and expression profiling of Oryza sativa nucleotidyl transferase protein (NTP) genes under various stress conditions.

Nucleotidyl transferase proteins (NTPs) modify the 3' ends of mature small RNAs, leading to their stabilization or degradation. The first two plant NTPs, HESO1 and URT1, were identified in Arabidopsis. These two NTPs act cooperatively to uridylate the 3' terminal nucleotide of specific miRNAs, leading to their degradation and thereby affecting the expression of genes regulated by these miRNAs. Little is known about NTPs in other plants. Here, we performed a comprehensive analysis of 13 putative NTP genes in Oryza sativa, a major crop in global food production. Phylogenetic analysis showed homology among the NTPs from diverse plant species. Analysis of cis-acting promoter elements at OsNTP loci identified several stress response elements, indicating the potential involvement of NTPs in plant stress responses. The promoter analysis results were validated by expression of the OsNTP genes under abiotic stress treatments, with some OsNTPs clearly induced by salt, drought or cold stress. Moreover, the RT-PCR data showed that the OsNTP genes were differentially expressed in different developmental stages and tissues. These findings suggest that NTPs, which are involved in small RNA metabolic pathways, might play roles in plant stress resistance.