Auxin represses stomatal development in dark-grown seedlings via Aux/IAA proteins

Abstract

Stomatal development is tightly regulated through internal and external factors that are integrated by a complex signalling network. Light represents an external factor that strongly promotes stomata formation. Here, we show that auxin-resistant aux/iaa mutants, e.g. axr3-1, exhibit a de-repression of stomata differentiation in dark-grown seedlings. The higher stomatal index in dark-grown axr3-1 mutants when compared with the wild type is due to increased cell division in the stomatal lineage. Excessive stomata in dark-grown seedlings were also observed in mutants defective in auxin biosynthesis or auxin perception and in seedlings treated with the polar auxin transport inhibitor NPA. Consistent with these findings, exogenous auxin repressed stomata formation in light-grown seedlings. Taken together, these results indicate that auxin is a negative regulator of stomatal development in dark-grown seedlings. Epistasis analysis revealed that axr3-1 acts genetically upstream of the bHLH transcription factors SPCH, MUTE and FAMA, as well as the YDA MAP kinase cascade, but in parallel with the repressor of photomorphogenesis COP1 and the receptor-like protein TMM. The effect of exogenous auxin required the ER family of leucine-rich repeat receptor-like kinases, suggesting that auxin acts at least in part through the ER family. Expression of axr3-1 in the stomatal lineage was insufficient to alter the stomatal index, implying that cell-cell communication is necessary to mediate the effect of auxin. In summary, our results show that auxin signalling contributes to the suppression of stomatal differentiation observed in dark-grown seedlings.

The miR393a/target module regulates seed germination and seedling establishment under submergence in rice (Oryza sativa L.)

“…Recently, auxin has been identified as a novel regulator of stomatal development (Balcerowicz et al . ; Le et al . ; Zhang et al .…”

“…The phenotype reported here is in contrast to a report on Arabidopsis , where loss‐of‐function mutations in multiple TIR1 / AFB auxin receptor genes resulted in stomata clustering and a moderate increase in stomatal number (Balcerowicz et al . ; Le et al . ; Zhang et al .…”

ERECTA family genes regulate development of cotyledons during embryogenesis

“…We speculate that inhibition of meristemoid differentiation is achieved in the earlier stages and does not require continuous expression of ERfs. Recently several papers have linked stomata differentiation after germination with auxin transport and signaling [23–25]. In the future it would be interesting to investigate whether ERf mediated inhibition of stomata differentiation during embryogenesis involves modification of auxin signaling or transport through components other then PIN1 and PIN3.…”

Polarity in plant asymmetric cell division: Division orientation and cell fate differentiation

“…The loss-of-function auxin transporter mutants pin2 3 4 7 and pin1 3 4 7 , similar to the receptor mutants tir1 afb1 2 3 , showed elevated stomatal index and clustered patterning, suggesting that auxin negatively regulates stomatal production (Le et al, 2014). This connection was further corroborated by Zhang et al (2014) and Balcerowicz et al (2014). The crosstalk between auxin signaling and the core stomatal development pathway is partially achieved by the activity of Auxin Response Factor (ARF) 5/MONOPTEROS (MP) that directly binds to the promoter of STOMAGEN and suppresses its expression (Zhang et al, 2014).…”

“…Contrary to the dominant roles of animal polarity proteins being almost entirely intrinsic cues, plant polarity proteins seem to participate in both intrinsic and extrinsic pathways to regulate divisional asymmetries in development. In addition, the phytoshormone auxin is recognized as an important regulator of ACD in multiple developmental contexts (Balcerowicz et al, 2014; Le et al, 2014; Zhang et al, 2014). This review mainly focuses on the current understanding of how ACD participating proteins and related signaling pathways are asymmetrically distributed in plant cells and how auxin activity in addition to these pathways may regulate physical asymmetry and differential identity in cell division.…”