SPEECHLESS Speaks Loudly in Stomatal Development

Abstract

Stomata, the small pores on the epidermis of plant shoot, control gas exchange between the plant and environment and play key roles in plant physiology, evolution, and global ecology. Stomatal development is initiated by the basic helix-loop-helix (bHLH) transcription factor SPEECHLESS (SPCH), whose central importance in stomatal development has recently come to light. SPCH integrates intralineage signals and serves as an acceptor of hormonal and environmental signals to regulate stomatal density and patterning during the development. SPCH also plays a direct role in regulating asymmetric cell division in the stomatal lineage. Owing to its importance in stomatal development, SPCH expression is tightly and spatiotemporally regulated. The purpose of this review is to provide an overview of the SPCH-mediated regulation of stomatal development, reinforcing the idea that SPCH is the central molecular hub for stomatal development.

RNA polymerase II associated proteins regulate stomatal development through direct interaction with stomatal transcription factors in Arabidopsis thaliana

“…Moreover, caterpillar‐like structures and unpaired GCs similar to those in fama and ice1 mutants were observed in the rima‐2 , amiR‐IYO and amiR‐QQT1 mutants. SPCH plays a central role in the control of stomatal lineage initiation (Chen et al ., 2020). On the one hand, SPCH can directly activate the expression of itself and SCRMs by binding to their promoters to promote stomatal lineage initiation.…”

Influence of Environmental Factors Light, CO2, Temperature, and Relative Humidity on Stomatal Opening and Development: A Review

“…Three basic-helix-loop-helix (bHLH) transcription factors are necessary and sufficient for driving the production of protodermal cells into stomata. These master transcription factors are SPEECHLESS (SPCH), MUTE, and FAMA [16] (Figure 1). These bHLH transcription factors are critical for the development of stomata, while mutation leads to the loss of correctly formed stomata [1,6,14].…”

“…In this negative feedback, SPCH directly binds and represses PIF4 expression ( Figure 6). SPCH represses PIF4 via the direct binding of PIF4's promoter [16,98]. This enables SPCH to accumulate sufficiently to ensure stomatal cell fate, as SPCH also plays a role in the spacing and amplifying division branches (Figure 1).…”

Beyond What Your Retina Can See: Similarities of Retinoblastoma Function between Plants and Animals, from Developmental Processes to Epigenetic Regulation

“…A similar mechanism is present in mammals, in which downregulation of MyoD allows cells to dedifferentiate; an ability that determines the muscular capacity to regenerate [ 219 ]. Finally, it is also possible that FAMA functions at early steps of guard cell differentiation since the AtRBR/FAMA heterodimer binds to SPCH and FAMA promoters, and this complex negatively regulates the accumulation of the SPCH transcript, which is normally expressed at early stages of guard cells development ( Figure 3 C) [ 211 , 220 ].…”