Light-Controlled Stomatal Opening and Development

 

 

Signaling Pathways in Plants

Machida Y., Lin C., Tamanoi F. (2014)

in Signaling Pathways in Plants, Vol. 35, 1st Ed., eBook ISBN: 9780128020159, Academic Press, 298 pp.,

in The Enzymes,

2.4 Light-Controlled Stomatal Opening and Development – 

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/stoma

Stomata regulate gas exchange between plants and atmosphere optimize the uptake of CO₂ and concomitant loss of water vapor [137]. It has been well known that light can trigger the opening of stomata even with very low irradiance, suggesting that the excited photoreceptors may mediate this response [138]. Blue light is well known for its strong activity in inducing stomata opening than red light [137,139]. The blue light-induced stomatal opening is primarily mediated by the blue-light receptors phototropins (PHOT1 and PHOT2) [140]. Independently of phototropins, cryptochromes may also be required for blue light-stimulated stomatal opening in Arabidopsis(Fig. 7.3A). Similar to phot1phot2, stomata of the cry1cry2 double mutants exhibited a reduced blue-light response, but this effect of cry1cry2 was relatively weaker than that of phot1phot2 [74]. Accordingly, overexpression of CRY1 caused a hypersensitivity to blue light [74]. Unlike phot1phot2, for which the stomatal opening response is insensitive to the fluence rate below 5 μmol m^− 2 s^− 1, the stomata of cry1cry2 are still able to respond to low fluence rate of blue light (> 1 μmol m^− 2 s^− 1), suggesting that cryptochromes are primarily functioned under high irradiance, while phototropins are functioned under a much wider fluence rates of blue light in terms of inducing stomatal opening [74]. Furthermore, the stomata of the cry1cry2 phot1phot2 quadruple mutants hardly open in response to any fluence rate of blue-light tested and this phenotype is apparently stronger than that of either phot1phot2 or cry cry2 double mutants, suggesting that cryptochromes work additively with phototropins in mediating blue light-induced stomata opening. This notion is also supported by the observation that overexpression of CRY1 in phot1phot2 rescued the blue light-insensitivity in this response [74]. Both the cryptochrome and phototropin signaling pathways in controlling stomata opening can be negatively regulated by constitutive photomorphogenic 1 (COP1) [74]. Earlier studies have demonstrated that COP1 interacts directly or indirectly with cryptochromes [124,141,142], but the biochemical relationship between COP1 and phototropins remains not very clear. Therefore, it will be interesting to investigate the different mechanisms of how CRY and PHOT modulate COP1 activity to regulate the stomatal opening in response to light at molecular level.

In addition to regulating stomatal opening, cryptochromes have been shown to be involved in blue light-induced stomatal development (Fig. 7.3B). The first evidence supporting this conclusion is that CRY1-overexpression led to dramatic clustered stomata in cotyledon epidermis under blue light [73]. Then an inhibited stomatal development is observed in cry1 cry2double mutants in a blue light-dependent manner [73]. These data indicate that cryptochromes are the primary photoreceptors mediating blue light-induced stomatal development of cotyledon epidermis. Genetic studies further demonstrate that the cryptochrome act antagonistically with the known stomatal development control pathways [73]. As in CRY-mediated de-etiolation, floral induction, and stomata opening responses, COP1 also acts genetically downstream of cryptochromes to regulate stomatal development [73]. But the exact molecular mechanism underlying this developmental response remains to be further studied.