Reactive Carbonyl Species Inhibit Blue-Light-Dependent Activation of the Plasma Membrane H+-ATPase and Stomatal Opening

A CRY1-HY5-MYB signaling cascade fine-tunes guard cell reactive oxygen species levels and triggers stomatal opening

Stomatal opening facilitates CO2 uptake and causes water loss via transpiration. Compared with the considerable progress made toward understanding phototropin-mediated blue light (BL) signaling in guard cells, the significance of cryptochromes (CRYs) in stomatal opening and their downstream elements remain largely unknown. Here, we show that 3 homologous MYB transcription factor genes, namely MYB11, MYB12, and MYB111, are rapidly transactivated in guard cells during the dark-to-light transition in Arabidopsis (Arabidopsis thaliana). Genetic characterization of myb mutants demonstrates that these proteins specifically mediate light-induced stomatal opening by promoting local flavonol accumulation, thereby controlling reactive oxygen species homeostasis in guard cells. In response to light, activation of the plasma membrane H+-ATPase is inhibited in the myb11 myb12 myb111 triple mutant, compromising transmembrane K+ influx in the mutant guard cells. Furthermore, we demonstrate that MYB11/12/111 expression in guard cells upon illumination is induced by a CRY1-specific signaling cascade involving ELONGATED HYPOCOTYL 5 (HY5), a direct transcriptional activator of these MYBs. Overall, our work reveals a mechanism by which the CRY1-HY5-MYB module facilitates light-induced stomatal opening, providing evidence that flavonoid metabolism in guard cells is crucial for plant stress tolerance.

Ribosome Pausing Negatively Regulates Protein Translation in Maize Seedlings during Dark-to-Light Transitions

Regulation of translation is a crucial step in gene expression. Developmental signals and environmental stimuli dynamically regulate translation via upstream small open reading frames (uORFs) and ribosome pausing. Recent studies have revealed many plant genes that are specifically regulated by uORF translation following changes in growth conditions, but ribosome-pausing events are less well understood. In this study, we performed ribosome profiling (Ribo-seq) of etiolated maize (Zea mays) seedlings exposed to light for different durations, revealing hundreds of genes specifically regulated at the translation level during the early period of light exposure. We identified over 400 ribosome-pausing events in the dark that were rapidly released after illumination. These results suggested that ribosome pausing negatively regulates translation from specific genes, a conclusion that was supported by a non-targeted proteomics analysis. Importantly, we identified a conserved nucleotide motif downstream of the pausing sites. Our results elucidate the role of ribosome pausing in the control of gene expression in plants; the identification of the cis-element at the pausing sites provides insight into the mechanisms behind translation regulation and potential targets for artificial control of plant translation.

Integration of light and ABA signaling pathways to combat drought stress in plants

Drought is one of the most critical stresses, which causes an enormous reduction in crop yield. Plants develop various strategies like drought escape, drought avoidance, and drought tolerance to cope with the reduced availability of water during drought. Plants adopt several morphological and biochemical modifications to fine-tune their water-use efficiency to alleviate drought stress. ABA accumulation and signaling plays a crucial role in the response of plants towards drought. Here, we discuss how drought-induced ABA regulates the modifications in stomatal dynamics, root system architecture, and the timing of senescence to counter drought stress. These physiological responses are also regulated by light, indicating the possibility of convergence of light- and drought-induced ABA signaling pathways. In this review, we provide an overview of investigations reporting light-ABA signaling cross talk in Arabidopsis as well as other crop species. We have also tried to describe the potential role of different light components and their respective photoreceptors and downstream factors like HY5, PIFs, BBXs, and COP1 in modulating drought stress responses. Finally, we highlight the possibilities of enhancing the plant drought resilience by fine-tuning light environment or its signaling components in the future.

Lipid-Derived Aldehydes: New Key Mediators of Plant Growth and Stress Responses

Aldehydes, derivatives of lipids, are ubiquitously produced through non-enzymatic and enzymatic pathways in higher plants and participate in many physiological and biological processes. Increasing evidence demonstrates that aldehydes are involved in plants response to many abiotic stresses, such as light, drought, heat and nutrient deficiency. In plant cells, endogenously triggered or exogenously applied high concentrations of aldehydes can damage proteins and nucleic acid, disturb redox homeostasis, and consequently inhibit plant growth; therefore, they are considered cytotoxins. Aldehyde levels are also used as biomarkers to evaluate the health status of plants. Further genetic research shows that several enzymes have strong capacities to detoxify these electrophilic aldehydes. Small molecules, such as carnosine and glutathione, also exhibit the ability to scavenge aldehydes, effectively promoting plant growth. Recently, increasing evidence has shown that certain aldehydes at certain concentrations can upregulate survival genes, activate antioxidant responses, increase defense against pathogens and stimulate plant growth. This review summarizes recent studies of lipid-derived aldehydes in higher plants, mainly focusing on the generation pathway, toxic effects, and detoxification strategies. In addition, the signaling effects of aldehydes in plants are also discussed.