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Plant resilience to drought stress requires a complex mechanism that involves controls of gene expression. Understanding its molecular regulation becomes critical to find the best strategy to improve plant tolerance to drought. Functional genomics has been a popular method to understand gene functions. In this study, an Ac/Ds transposon-mediated mutant library has been constructed previously to identify genes that might be involved in regulating drought tolerance in rice. From the screening activities of the mutant library using PEG6000 treatments, a mutant line has been selected as one of the drought-tolerant candidates. Further analysis was done to identify the location of Ds transposon in the rice genome. After performing a TAIL-PCR method, one of the flanking regions of Ds insertion was isolated, cloned, and sequenced. It was revealed that the Ds transposon element had been inserted into the last exon of a gene from the family of pentatricopeptide repeat protein (PPR) located at chromosome 11. Interestingly, a sequence of a putative natural antisense transcript (NAT) was also identified in the reverse direction of this gene. From a survey through bioinformatics, five genes were found to be located nearby the insertion site, including Os11g0131200, Os11g0131300, Os11g0131400, Os11g0131500, and Os11g0131600. However, most of these genes have not been functionally characterized in rice. Further investigations are still needed to reveal which gene plays the key role in the tolerance mechanism and whether disruption of the NAT sequence affects rice tolerance to drought. [ABSTRACT FROM AUTHOR]