Differential expression of genes related to tillering in lowland rice varieties cultivated under upland condition

Abstract

Rice tillering is a key determinant of yield and is influenced by genetic, hormonal, and environmental factors. Building upon previous findings that upland conditions reduced tiller production in lowland rice varieties, this study investigated the differential expression of tillering-related genes in two lowland rice varieties, Kadaria and MR269, cultivated under upland and lowland conditions. The transcript abundance of genes involved in tillering, phytohormone biosynthesis, and stress response at the basal part of the rice plant was analyzed using the NanoString nCounter® system. The down-regulation of PIN Protein 9 (OsPIN9) and up-regulation of Dwarf 14 (D14) in both lowland rice varieties may lead to auxin accumulation and enhanced strigolactone signaling in rice plants cultivated under upland conditions, hence causing them to produce fewer tillers. In addition, the up-regulation of Cytochrome P450 735A4 (CYP735A4), a gene involved in cytokinin biosynthesis, was also observed in rice plants cultivated under upland conditions. The differential expression of LAX Panicle 2 (LAX2), PIN Protein 1b (OsPIN1b), PIN Protein 2 (OsPIN2), and Pyrabactin Resistance 1 Like/Regulatory Components of ABA Receptor 10 (OsPYL/RCAR10) was unique to specific rice varieties, suggesting varietal differences in tillering responses to a possible water stress imposed by the upland conditions. These findings contribute to the understanding of potential molecular pathways influencing tiller production in lowland rice varieties cultivated under water-limited upland conditions.