Integrative transcriptomic and physiological analysis uncovers subspecies-preferred regulatory mechanisms of mercury tolerance in Indica and Japonica rice

Le résumé fourni par la source

Mercury (Hg) is a widespread heavy metal pollutant that threatens the safe production of rice, yet the molecular responses of the two major rice subspecies, indica and japonica , to Hg stress remain inadequately characterized. Here, we integrated physiological and biochemical analyses with root transcriptome sequencing to compare the response strategies of indica (NH701, N1311R) and japonica (NHH, WN) seedlings exposed to Hg stress. Although Hg exposure markedly inhibited growth and induced oxidative damage in both subspecies, Hg-tolerant genotypes maintained greater growth vigor and retained more Hg in roots than sensitive genotypes, with the highest capacity observed in the tolerant indica cultivar. Transcriptome profiling revealed that “glutathione metabolism” and “phenylpropanoid biosynthesis” were core pathways activated in both subspecies. However, their downstream defense strategies exhibited subspecies-preferred patterns. Japonica preferentially reinforced peroxidase-mediated antioxidant systems and lignin biosynthesis to strengthen cell wall barriers. In contrast, indica coordinately upregulated sulfur assimilation and glutathione metabolism, enhanced ABC transporter-mediated vacuolar sequestration, and modulated ZIP family metal transporters as part of a basal transcriptional response, collectively restricting Hg detoxification and retention. Weighted gene co-expression network analysis further identified OsWRKY24 (Os01g0826400) , OsNAC4 (Os01g0816100) , and OsHSFA4D (Os05g0530400) as hub transcription factors that may orchestrate these subspecies-preferred regulatory networks. Collectively, our findings uncover characteristic detoxification strategies in rice under Hg stress: a “chelation-sequestration” mode in indica and a “barrier-antioxidation” mode in japonica . These results advance understanding of the genetic basis underlying subspecific variation in heavy metal adaptation and provide a theoretical framework and candidate targets for breeding low-Hg-accumulating rice cultivars.

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