Abstract
Stomatal movements are regulated by many environmental signals, such as light, CO2, temperature, humidity, and drought. Recently, we showed that photoperiodic flowering components have positive effects on light-induced stomatal opening in Arabidopsis thaliana. In this study, we determined that light-induced stomatal opening and increased stomatal conductance were larger in plants grown under long-day (LD) conditions than in those grown under short-day (SD) conditions. Gene expression analyses using purified guard cell protoplasts revealed that FT and SOC1 expression levels were significantly increased under LD conditions. Interestingly, the enhancement of light-induced stomatal opening and increased SOC1 expression in guard cells due to LD conditions persisted for at least 1 week after plants were transferred to SD conditions. We then investigated histone modification using chromatin immunoprecipitation–PCR, and observed increased trimethylation of lysine 4 on histone 3 (H3K4) around SOC1. We also found that LD-dependent enhancement of light-induced stomatal opening and H3K4 trimethylation in SOC1 were suppressed in the ft-2 mutant. These results indicate that photoperiod is an important environmental cue regulating stomatal opening, and that LD conditions enhance light-induced stomatal opening and epigenetic modification (H3K4 trimethylation) around SOC1, a positive regulator of stomatal opening, in an FT-dependent manner. Thus, this study provides novel insights into stomatal responses to photoperiod.
Highlights
Plants need stomata in the plant epidermis for gas exchange between plants and the atmosphere, providing CO2 uptake for photosynthesis, O2 efflux, and transpiration
Recent studies have indicated that mRNAs of photoperiodic flowering components, such as GIGANTEA (GI), CONSTANS (CO), FLOWERING LOCUS T (FT), TWIN SISTER OF FT (TSF), and SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1), are exist in guard cells and these components positively enhance light-induced stomatal opening in A. thaliana[13,14,15]
We investigated the effect of photoperiod on light-induced stomatal opening in A. thaliana and found that LD conditions enhanced light-induced stomatal opening and SOC1 expression via FT and increased expression level of a plasma membrane (PM) H+-ATPase isoform, AHA5, in guard cells
Summary
To clarify the effects of photoperiod on stomatal opening in response to light, we investigated light-induced stomatal opening in plants grown under LD and SD conditions. We found that the LD-dependent increase in SOC1 expression was severely suppressed in guard cell-enriched epidermal fragments from the ft-2 mutant (Fig. 2a) Together, these results suggest that SOC1 is involved in LD-dependent enhancement of light-induced stomatal opening downstream of FT. SOC1 overexpression in guard cells enhances light-induced stomatal opening and increases expression levels of plasma membrane (PM) H+-ATPase isoforms[15]. We investigated SOC1 expression levels in guard cell-enriched epidermal fragments from SSS, in which plants were grown under SD conditions for 6 weeks (Fig. 1a), SLL, and SLS plants using qRT-PCR. FT expression was lower in SLS plants (Fig. 3b) These results suggest that guard cells of SLS plants memorize FT-dependent enhancement of light-induced stomatal opening and SOC1 expression under LD conditions for at least 1 week, even after returning to SD conditions. The ft-2 mutant did not exhibit LD-dependent enhancement of H3K4 trimethylation on SOC1 in guard cell-enriched epidermal fragments from
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