Two Arabidopsis MYB-SHAQKYF transcription repressors regulate leaf wax biosynthesis via transcriptional suppression on DEWAX.

Plant cuticular wax accumulation limits nonstomatal transpiration and is regulated by external environmental stresses. DEWAX (DECREASE WAX BIOSYNTHESIS) plays a vital role in diurnal wax biosynthesis. However, how DEWAX expression is controlled and the molecular mechanism of wax biosynthesis regulated by the diurnal cycle remains largely unknown. Here, we identified two Arabidopsis MYB-SHAQKYF transcription factors, MYS1 and MYS2, as new regulators in wax biosynthesis and drought tolerance. Mutations of both MYS1 and MYS2 caused significantly reduced leaf wax, whereas overexpression of MYS1 or MYS2 increased leaf wax biosynthesis and enhanced drought tolerance. Our results demonstrated that MYS1 and MYS2 act as transcription repressors and directly suppress DEWAX expression via ethylene response factor-associated amphiphilic repression motifs. Genetic interaction analysis with DEWAX, SPL9 (SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 9), and CER1 (ECERIFERUM 1) in wax biosynthesis and under drought stresses demonstrated that MYS1 and MYS2 act upstream of the DEWAX-SPL9 module, thus regulating CER1 expression. Expression analysis suggested that the diurnal expression pattern of DEWAX is partly regulated by MYS1 and MYS2. Our findings demonstrate the roles of two unidentified transcription repressors, MYS1 and MYS2, in wax biosynthesis and provide insights into the mechanism of diurnal cycle-regulated wax biosynthesis.

Stomatal maturomics: hunting genes regulating guard cell maturation and function formation from single-cell transcriptomes.

Stomata play critical roles in gas exchange and immunity to pathogens. While many genes regulating early stomatal development up to the production of young guard cells (GCs) have been identified in Arabidopsis, much less is known about how young GCs develop into mature functional stomata. Here we perform a maturomics study on stomata, with "maturomics" defined as omics analysis of the maturation process of a tissue or organ. We develop an integrative scheme to analyze three public stomata-related single-cell RNA-seq datasets and identify a list of 586 genes that are specifically up-regulated in all three datasets during stomatal maturation and function formation. The list, termed sc_586, is enriched with known regulators of stomatal maturation and functions. To validate the reliability of the dataset, we selected two candidate G2-like transcription factor genes, MYS1 and MYS2, to investigate their roles in stomata. These two genes redundantly regulate the size and hoop rigidity of mature GCs, and the mys1 mys2 double mutants cause mature GCs with severe defects in regulating their stomatal apertures. Taken together, our results provide a valuable list of genes for studying GC maturation and function formation.