Plasticity in stomatal development: what role does MAPK signaling play?

Abstract

Stomata are specialized pores found on the epidermal surface of many aerial tissues of plants, where they function to regulate the exchange of gases such as carbon dioxide and water vapor between the plant and its environment. This makes stomatal complexes essential for the survival of the plant; a complete loss of stomata is lethal. On a global level, stomatal regulation of gas exchange makes stomata critical regulators of carbon and water cycles, while on an organismal level, stomatal development is flexible in that the ultimate distribution of stomata can be controlled by environmental stimuli. (1) While several environmental factors capable of influencing stomatal development have been identified, the molecular mechanisms mediating this flexibility have remained elusive. Recent studies suggest that this plasticity involves an expanding collection of mitogen activated protein kinase (MAPK) signaling components and putative upstream extracellular ligands. (2,3) Furthermore, it appears that stomatal development and distribution may not be the result of a simple "on/off" switch regulating lineage entry. Rather, stomatal precursors in Arabidopsis can be influenced at multiple points in the well-characterized stomatal development pathway by modulation of a core MAPK signaling module. (3.)

Natural variation in stomatal abundance of Arabidopsis thaliana includes cryptic diversity for different developmental processes

“…However, the broad geographic distribution of the accessions studied and imprecise information on their original habitats may influence these findings. In addition, given the high plasticity of the traits studied ( Casson and Gray, 2008 ; Lampard, 2010 , and references therein), phenotypes may differ between laboratory conditions and natural environments, fading a putative adaptive basis in the underlying genetic variation.…”

“…Primary and satellite stomatal pathways are assumed to contribute to the phenotypic plasticity of A. thaliana stomatal development in response to internal and environmental cues ( Bergmann and Sack, 2007 ; Casson and Gray, 2008 ; Lampard, 2010 ), but whether each pathway displays specific responses remains to be established. Unravelling the molecular genetic basis of the observed variation would shed light on a basic developmental programme, and may also provide tools to understand plant productivity under different environments.…”

A Genetic Dissection of Natural Variation for Stomatal Abundance Traits in Arabidopsis

“…Therefore, MID3 and ER might also impinge on SL initiation through still undescribed pathways. It has been assumed that PL and SL contribute to the phenotypic plasticity of stomatal development in response to internal and environmental signals (Bergmann and Sack, 2007; Casson and Hetherington, 2010; Lampard, 2010). Supporting this view, recent work on the stomatal development responses (Haus et al, 2018) highlights the importance of SL in developmental plasticity in response to the atmospheric CO 2 concentration.…”

Overexpression of PagSTOMAGEN, a Positive Regulator of Stomatal Density, Promotes Vegetative Growth in Poplar

“…Stomatal density is regulated by positive and negative genetic factors [ 11 , 12 ]. Negative regulators include the cell surface receptor TOO MANY MOUTHS ( TMM ) [ 13 ], ERECTA family receptor-like kinases ( ER , ERL1 , and ERL2 ) [ 14 ] and their ligands EPF1 and EPF2 [ 15 , 16 , 17 ], as well as STOMATAL DENSITY AND DISTRIBUTION 1 ( SDD1 ) functioning in a TMM -dependent manner [ 18 , 19 ]. Positive regulators include the three core bHLH transcriptional regulators SPEECHLESS , MUTE , and FAMA [ 20 , 21 , 22 ], and STOMAGEN/EPFL9 ( STOMAGEN ) belonging to the EPF/EPFL family [ 23 ].…”