Cryptochromes, Phytochromes, and COP1 Regulate Light-Controlled Stomatal Development inArabidopsis 

Abstract

In Arabidopsis thaliana, the cryptochrome (CRY) blue light photoreceptors and the phytochrome (phy) red/far-red light photoreceptors mediate a variety of light responses. COP1, a RING motif-containing E3 ubiquitin ligase, acts as a key repressor of photomorphogenesis. Production of stomata, which mediate gas and water vapor exchange between plants and their environment, is regulated by light and involves phyB and COP1. Here, we show that, in the loss-of-function mutants of CRY and phyB, stomatal development is inhibited under blue and red light, respectively. In the loss-of-function mutant of phyA, stomata are barely developed under far-red light. Strikingly, in the loss-of-function mutant of either COP1 or YDA, a mitogen-activated protein kinase kinase kinase, mature stomata are developed constitutively and produced in clusters in both light and darkness. CRY, phyA, and phyB act additively to promote stomatal development. COP1 acts genetically downstream of CRY, phyA, and phyB and in parallel with the leucine-rich repeat receptor-like protein TOO MANY MOUTHS but upstream of YDA and the three basic helix-loop-helix proteins SPEECHLESS, MUTE, and FAMA, respectively. These findings suggest that light-controlled stomatal development is likely mediated through a crosstalk between the cryptochrome-phytochrome-COP1 signaling system and the mitogen-activated protein kinase signaling pathway.

Auxin inhibits stomatal development through MONOPTEROS repression of a mobile peptide gene STOMAGEN in mesophyll

“…Thus, it was proposed that EPFs are a novel class of peptide hormones (32, 33). Although intrinsic program regulating stomatal development has been well characterized, how the top signals from EPFs are regulated remains elusive.Phytohormones and external stimuli, such as brassinosteroids (BRs), light, and carbon dioxide, are also involved in modulating stomatal production (13,14,(34)(35)(36). Here we show that nuclear receptor-mediated auxin signaling negatively regulates stomatal development, and that ARF5/MONOPTEROS (MP) is involved in regulating this process.…”

A Gain-of-Function Mutation of Arabidopsis CRYPTOCHROME1 Promotes Flowering

“…Absorption of light would then cause conformational changes of the PHR domain, leading to release of the CCT domain, which could eventually activate the signaling chain (for review, see Lin and Todo, 2005). Because cry1 functions at least partially by affecting the ability of COP1 to ubiquitinate target proteins, which will then be degraded by the proteasome (Wang et al, 2001;Yang et al, 2001;Jang et al, 2008;Liu et al, 2008b;Kang et al, 2009), it is possible that cry1-L407F attenuates COP1 activity. This would lead to increased accumulation of HY5, causing light hypersensitivity of seedlings.…”

Stomatal Development in Arabidopsis

“…The regulation of stomatal movement is coordinately controlled by a large network of signaling pathways that monitor water status, light, CO 2 and various other environmental conditions to optimize plant growth and water use (Schroeder et al, 2001;Shimazaki et al, 2007;Casson and Hetherington, 2010;Tricker et al, 2012). Numerous Arabidopsis mutants have been isolated that are defective in stomatal function (Gray et al, 2000;Assmann, 2003;Miyazawa et al, 2006;Young et al, 2006;Kang et al, 2009a;Clark et al, 2011;Sawinski et al, 2013).…”

“…The binding of phyB to PIF4 might influence the interaction strength of PIF4 with other bHLHs (Casson et al, 2009) (Figure 11). In addition to phyB, the blue-light receptors, CRYPTOCHROME1 (CRY1: At4g08920) and CRY2 (At1g04400), and the red/far-red photoreceptor, phytochrome A (phyA: At1g09570), all act to promote stomata production under high light intensity (Kang et al, 2009a). The link between light signaling and stomatal development is through the E3 ubiquitin-protein ligase, CONSTITUTIVE PHOTOMORPHO-GENIC 1 (COP1: At2g32950), a well-known repressor of lightmediated development.…”