Jasmonate Negatively Regulates Stomatal Development in Arabidopsis Cotyledons

Stomata are ports that facilitate gas and water vapor exchange between plants and their environment. Stomatal development is strictly regulated by endogenous signals and environmental cues. Jasmonate is an important signal that modulates multiple physiological processes in plants, yet the molecular mechanisms underlying its interactions with other developmental signaling pathways remain poorly understood. Here, we show that jasmonate negatively regulates stomatal development in Arabidopsis (Arabidopsis thaliana) cotyledons. Cotyledons of the wild type and stomata-overproliferating mutants (such as too many mouths-1 and stomatal density and distribution1-1) treated with methyl jasmonate exhibit a clear reduction in stomata number. By contrast, blocking endogenous jasmonate biosynthesis or perception enhanced stomatal development. Moreover, three MYC transcription factors involved in jasmonate signaling, MYC2, MYC3, and MYC4, were found to redundantly modulate jasmonate-inhibited stomatal development. A genetic analysis showed that these MYC proteins act upstream of the SPEECHLESS and FAMA transcription factors to mediate stomatal development. Furthermore, jasmonate repression of stomatal development is dependent on these three MYC transcription factors, as stomatal development of the myc2 myc3 myc4 triple mutant was insensitive to methyl jasmonate treatment. Collectively, our study demonstrates that jasmonate and MYC transcription factors negatively regulate stomatal development in Arabidopsis cotyledons.