Find in Library

Mining the key genes involved in the balance of rice salt tolerance is extremely important for developing salt-tolerant rice varieties. A library of <i>japonica</i> mutants was screened under salinity conditions to identify putative salt stress-responsive genes. We identified a highly salt-sensitive mutant <i>ss3</i> and used a map-based cloning approach to isolate the gene <i>SS3</i>, which encodes mannose-1-phosphate guanylyltransferase. Under salt treatment, <i>ss3</i> mutants have decreased ascorbic acid (AsA) content and increased reactive oxygen species (ROS) levels compared with the wild type (WT). Exogenous AsA restored the salt tolerance of <i>ss3</i> plants, indicating that inhibition of AsA synthesis was an important factor in the salt sensitivity of the mutant. Functional complementation using the WT allele rescued the mutation, and transcription of <i>SS3</i> was induced by salt stress. Vector <i>SS3p:SS3</i> was constructed containing the 1086 bp coding sequence of <i>SS3</i>. Under salinity conditions, transgenic seedlings expressing <i>SS3p:SS3</i> had improved salt tolerance relative to WT, as demonstrated by better growth status, higher chlorophyll content, a lower level of Na⁺, and a reduced Na⁺/K⁺ ratio. Further investigation revealed that several senescence- and autophagy-related genes were expressed at lower levels in salt-stressed transgenic lines compared to WT. These results demonstrate the positive impact of <i>SS3</i> on salt tolerance in rice through the regulation of AsA synthesis and ROS accumulation, and indicate that <i>SS3</i> is a valuable target for genetic manipulation.