Rice Transcription Factor HSTL Regulates Plant Height and Salt Stress Response by Modulating Gibberellin Homeostasis

Gibberellins (GAs) are crucial in the regulation of plant growth and development, and in responses to adverse environments. Here, we report that a Cys2 /His2 zinc finger protein in rice, HSTL (heat stress tolerance like), participates in the control of stem elongation and salt stress response by affecting GA homeostasis. Knockdown of HSTL increased plant height, internode elongation and bioactive GAs levels in rice plants. Comparative transcriptome showed that HSTL plays a critical role in rice GA pathway through regulation of genes involved in GA biosynthesis and metabolism. In addition, HSTL knockdown seedlings maintained higher relative water content and lower accumulation of H₂O₂ as well as higher tolerance to salt stress compared with the wild-type (WT). These results suggest that HSTL plays an important role in regulating internode elongation and stress response by coordinating GAs homeostasis, thus providing a useful target for engineering stress-tolerant rice varieties.