SlIAA9 Gene Identified as Heat Resilience Regulator in Tomato
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- University of Tsukuba researchers showed that tomato mutants lacking the SlIAA9 gene maintained high germination rates under high-temperature conditions and developed largely normal seedlings, while wild-type tomatoes suffered markedly reduced germination, shortened shoots and roots, and high rates of abnormal morphology.
- SlIAA9, an auxin signaling repressor involved in regulating seed germination, was identified as a negative regulator of seed heat resilience, with its loss-of-function boosting expression of antioxidant enzyme genes (which detoxify heat-induced reactive oxygen species) and enhancing induction of the heat shock protein HSP70.
- SlIAA9 mutant seeds showed attenuated responsiveness to abscisic acid, a hormone that enforces seed dormancy, while genes involved in ethylene biosynthesis — a pathway that promotes germination and post-stress recovery — were more strongly activated in mutants than in wild-type seeds under heat stress.
- Bayu Pradana Nur Rahmat et al. published the findings in Plant Physiology and Biochemistry (2026) under DOI 10.1016/j.plaphy.2026.111103, testing two independent SlIAA9 loss-of-function mutant lines against wild-type controls.
- Targeted modulation of SlIAA9 function may serve as a genetic strategy for breeding crop varieties with stable germination and early growth in increasingly high-temperature environments, the researchers concluded.
Why it matters: High-temperature exposure routinely causes thermo-dormancy in tomato seeds, threatening seedling establishment and yields as global temperatures rise. Pinpointing SlIAA9 as a negative regulator gives plant breeders a concrete genetic target — and potentially a transferable mechanism across other crops — to engineer varieties that germinate reliably under heat stress.
