IDD16 negatively regulates stomatal initiation via trans‐repression of SPCH in Arabidopsis

Abstract

Summary In Arabidopsis , the initiation and proliferation of stomatal lineage cells is controlled by SPEECHLESS ( SPCH ). Phosphorylation of SPCH at the post‐translational level has been reported to regulate stomatal development. Here we report that IDD 16 acts as a negative regulator for stomatal initiation by directly regulating SPCH transcription. In Arabidopsis , IDD 16 overexpression decreased abaxial stomatal density in a dose‐dependent manner. Time course analysis revealed that the initiation of stomatal precursor cells in the IDD 16 ‐ OE plants was severely inhibited. Consistent with these findings, the transcription of SPCH was greatly repressed in the IDD 16 ‐ OE plants. In contrast, IDD 16‐ RNA i transgenic line resulted in enhanced stomatal density, suggesting that IDD 16 is an intrinsic regulator of stomatal development. Ch IP analysis indicated that IDD 16 could directly bind to the SPCH promoter. Furthermore, Arabidopsis plants overexpressing IDD 16 exhibited significantly increased drought tolerance and higher integrated water use efficiency ( WUE ) due to reduction in leaf transpiration. Collectively, our results established that IDD 16 negatively regulates stomatal initiation via trans‐repression of SPCH , and thus provide a practical tool for increasing plant WUE through the manipulation of IDD 16 expression.

SlTLFP8 reduces water loss to improve water‐use efficiency by modulating cell size and stomatal density via endoreduplication

“…Leaves from three independent lines of T 3 transgenic plants harbouring SlTLFP8 pro::GUS were used to analyse the activity of GUS, as described previously (C. Qi et al, 2019).…”

“…The 6‐week‐old tomato seedlings were used to measure water loss rate as described previously (C. Qi et al, 2019). The experiment was preformed three times, three plants were used for each replication.…”

“…Electrolyte leakage and the content of malondialdehyde (MDA) as indicators of lipid peroxidation were measured as described previously (C. Qi et al, 2019). For electrical leakage, leaves were chopped and incubated with deionized water in a tube for 4 hr, and the electrical conductivity 1 (EC1) was measured using an Acromet AR20 electrical conductivity metre (Fisher Scientific, Chicago, IL).…”

SPEECHLESS Speaks Loudly in Stomatal Development

“…A microRNA pathway is presumed to repress stomatal lineage initiation through regulating SPCH transcripts ( Figure 2) (Kutter et al, 2007;Yang et al, 2014). In addition, IDD16, a C2H2 zinc finger transcription factor from the INDETERMINATE DOMAIN (IDD) family, and RETINOBLASTOMA RELATED (RBR), which is targeted by CDKA;1, have been shown to inhibit stomatal initiation by directly binding to SPCH and repressing SPCH transcription ( Figure 2) (Weimer et al, 2012;Qi et al, 2019). The specific downregulation of RBR in GMCs and GCs leads to excess divisions in differentiated GCs and formation of the "Stoma-in-Stoma" (SIS) phenotype (Lee et al, 2014b;Matos et al, 2014).…”

SPEECHLESS and MUTE Mediate Feedback Regulation of Signal Transduction during Stomatal Development

“…Conversely, the IDD16-RNAi transgenic line exhibited increased stomatal density, demonstrating that IDD16 is an intrinsic stomatal development regulator. Furthermore, ChIP analysis results showed that IDD16 could bind the promoter of SPCH [85]. With respect to the other eight down-regulated genes (MUTE, FAMA, TMM, SDD1, EPF1, EPF2, BA-SAL, and POLAR), which are expressed explicitly in MMC, meristemoid cells, GMCs, and GCs are attributed to reduced stomatal precursor cells development in IDD16-OE plants [85].…”