SlERF36, an EAR-motif-containing ERF gene from tomato, alters stomatal density and modulates photosynthesis and growth

The AP2 domain class of transcription factors is a large family of genes with various roles in plant development and adaptation but with very little functional information in plants other than Arabidopsis. Here, the characterization of an EAR motif-containing transcription factor, SlERF36, from tomato that affects stomatal density, conductance, and photosynthesis is described. Heterologous expression of SlERF36 under the CaMV35S promoter in tobacco leads to a 25-35% reduction in stomatal density but without any effect on stomatal size or sensitivity. Reduction in stomatal density leads to a marked reduction in stomatal conductance (42-56%) as well as transpiration and is associated with reduced CO₂ assimilation rates, reduction in growth, early flowering, and senescence. A prominent adaptive response of SlERF36 overexpressors is development of constitutively high non-photochemical quenching (NPQ) that might function as a protective measure to prevent damage from high excitation pressure. The high NPQ leads to markedly reduced light utilization and low electron transport rates even at low light intensities. Taken together, these data suggest that SlERF36 exerts a negative control over stomatal density and modulates photosynthesis and plant development through its direct or indirect effects.