LAUSR

The phytohormones ethylene and jasmonate play important roles in the adaption of rice plants to salt stress. However, the molecular interactions between ethylene and jasmonate on rice seminal root growth under salt stress is unknown. In this study, effects of NaCl on the homeostasis of ethylene and jasmonate and on the rice seminal root growth were investigated. Our results indicate that NaCl treatment promotes ethylene biosynthesis by up-regulating transcription of ethylene biosynthesis genes, whereas NaCl-induced ethylene cannot inhibit rice seminal root growth directly, but rather inhibits growth indirectly by promoting jasmonate biosynthesis. NaCl treatment also promotes jasmonate biosynthesis through an ethylene-independent pathway. Moreover, the analysis results of quantitative real-time PCR and confocal microscopy demonstrate that NaCl-induced jasmonate restricts root meristem cell proliferation by reducing meristem cell number and cell division activity via down-regulated transcription of OsPLT and cell division-related genes, respectively. Additionally, NaCl-induced jasmonate inhibits root cell elongation by down-regulating transcription of cell elongation-related genes, which in turn inhibits seminal root growth. Overall, salt stress promotes jasmonate biosynthesis through ethylene-dependent and -independent pathways in the rice seminal root, and salt-induced jasmonate inhibits the rice seminal root growth by inhibiting root meristem cell proliferation and root cell elongation under salt stress.