Arabidopsis JINGUBANG is a negative regulator of pollen germination that prevents pollination in moist environments

Abstract

The molecular mechanism of pollen germination and pollen tube growth has been revealed in detail during the last decade, while the mechanism that suspends pollen grains in a dormant state is largely unclear. Here, we identified the JINGUBANG (JGB) gene by screening pollen-specific genes for those that are unnecessary for pollen germination. We showed that the pollen of the jgb loss-of-function mutant exhibited hyperactive germination in sucrose-only medium and inside the anther, while this phenotype was rescued by the transgenic expression of JGB in jgb plants. JGB contains seven WD40 repeats and is highly conserved in flowering plants. Overexpression of JGB inhibits pollen germination. These results indicate that JGB is a novel negative regulator of pollen germination. In addition, we found that jasmonic acid (JA) abundance was significantly elevated in jgb pollen, while exogenous application of methyl jasmonate rescued the inhibition of pollen germination in plants overexpressing JGB. Based on the molecular features of JGB and on the finding that it interacts with a known JA biosynthesis-related transcription factor, TCP4, we propose that JGB, together with TCP4, forms a regulatory complex that controls pollen JA synthesis, ensuring pollination in moist environments.