A role for Arabidopsis cryptochromes and COP1 in the regulation of stomatal opening

Abstract

blue light photoreceptor ͉ phototropin ͉ water evaporation ͉ photosynthesis T he stomatal pores of higher plants act as ports that tightly regulate the uptake of CO 2 for photosynthesis and the evaporation of water for transpiration. Situated in the epidermis, they are surrounded by a pair of guard cells, which regulate their opening in response to environmental and internal signals, including light, humidity, CO 2 , phytohormones, calcium, and reactive oxygen species (1-5). Stomata are closed in darkness but open in response to blue light.Blue light responses are primarily mediated by four blue light photoreceptors in Arabidopsis: cryptochrome (CRY)1, CRY2, phototropin (PHOT)1, and PHOT2. Major blue light responses mediated by CRY1 and CRY2 include inhibition of hypocotyl elongation (6-8), enhancement of cotyledon expansion (9), anthocyanin accumulation (8, 10, 11), and regulation of flowering time (12-15). CRY1 and CRY2, together with the red͞ far-red light receptor phytochromes, also serve to entrain the circadian clock (16). There is now evidence for a third CRY (CRY3) in Arabidopsis, the role of which is presently unknown (17). PHOT1 and PHOT2 work together to mediate phototropism, blue light-induced chloroplast migration, and blue lightdependent regulation of stomatal opening (18)(19)(20)(21)(22). Recent studies have shown that CRY and PHOT perform overlapping roles. For examples, PHOT functions at early stages to regulate photomorphogenic development, including rapid inhibition of hypocotyl elongation (23) and enhancement of cotyledon expansion (24), and CRY and PHOT function together to enhance phototropism under low fluence rate blue light (25).Insight into the signaling mechanism of Arabidopsis CRY was obtained through the demonstration that transgenic plants expressing the C-terminal domain of either CRY1 (CCT1) or CRY2 (CCT2) fused to ␤-glucuronidase (GUS) display a constitutive photomorphogenic (COP) phenotype (11), which is similar to that of mutants of both COP1 and COP9 signalosome, the negative regulators of photomorphogenesis (26,27). Both CCT1 and CCT2 were shown to bind to COP1 (28,29), indicating that the signaling mechanism of Arabidopsis CRY1 and CRY2 is mediated through negative regulation of COP1 by direct CRY-COP1 interaction. It is now demonstrated that Arabidopsis CRY1 N-terminal domain mediates homodimerization, which is required for light activation of CCT1 (30).The purpose of the present study was to determine the role of the Arabidopsis CRY and COP1 signaling system in the regulation of stomatal opening. Through molecular, genetic, and physiological analyses, we demonstrate that CRY acts additively with PHOT to mediate blue light-induced stomatal opening and that COP1 is a repressor of stomatal opening and likely acts downstream of CRY and PHOT signaling pathways. Materials and MethodsExperimental procedures of construction of expression cassettes and transformation, antibody production, PCR, Western blot, and construction of the various double, triple, and quadruple mutants can b...

Significant improvement of stress tolerance in tobacco plants by overexpressing a stress-responsive aldehyde dehydrogenase gene from maize (Zea mays)

“…A 1878-bp HindIII/BamHI ZmALDH22A1 cDNA fragment with 18 bp of 5 0 -untranslated leader and 78 bp of 3 0 -untranslated trailer was subcloned into the plant gene expression vector pHB, which contains a double CaMV 35S promoter and the rbcS polyadenylation signal (Mao et al 2005). The resultant construct was named as pHB-087 and introduced into Agrobacterium tumefaciens EHA105.…”

Membrane Proteomic Analysis of Arabidopsis thaliana Using Alternative Solubilization Techniques

“…Both D1 and D2 are synthesized under the control of chloroplast machinery and Figures 3B and 4). COP1 interaction protein (At5g43310), a repressor of photomorphogenesis in darkness and stomatal opening 48 has one TMD and was identified using both methods (Table 4). DWARF1 (DWF1, At3g19820), only identified by the methanol approach (Table 3), has one putative TMD and is involved in the conversion of the early brassinosteroid precursor 24-methylenecholesterol to campesterol.…”

Arabidopsis STO/BBX24 negatively regulates UV-B signaling by interacting with COP1 and repressing HY5 transcriptional activity

“…Triple mutants of bbx24 with different photoreceptor mutants were made by crossing bbx24 to the double mutants of phyA-211 phyB-9, phot1-5 phot2-1, and cry1-104 cry2-1 [36,37]. The F2 seedlings were screened under either blue or red light, and seedlings with long hypocotyls were selected according to previous phenotypic analysis [16].…”