Overexpression of cytosolic‐malic enzyme 1 from the common ice plant enhances water‐deficit and high‐light stress tolerance by modulating water‐use efficiency and flavonoid biosynthesis
Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine
SUMMARY Innovative strategies are essential to enhance crop resilience against drought and heat stress intensified by climate change. Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway that improves water‐use efficiency (WUE) by shifting COfixation to the nighttime. The common ice plant () utilizes NADP‐malic enzymes (ME) for malate decarboxylation during its facultative CAM transition. In this study, we characterized the cytosolicenzyme, which is highly expressed in the ice plant under water‐deficit stress. Transgenicplants overexpressingexhibited reduced stomatal density, size, and conductance, leading to enhanced instantaneous WUE. Although these modifications resulted in reduced biomass and seed yield under low‐light conditions, the transgenic lines showed significantly improved survival and growth under both acute and chronic water‐deficit stress. Additionally,overexpression conferred improved vegetative growth under high‐light stress conditions. Notably,overexpression upregulated many genes within the flavonoid biosynthetic pathway, resulting in a marked increase in total flavonoid content. These flavonoids acted as effective antioxidants that facilitated the scavenging of reactive oxygen species (ROS), thereby reducing oxidative damage and malondialdehyde (MDA) levels under both water‐deficit and high‐light stress conditions. These results demonstrate that cytosolicis a key enzyme for conferring water‐deficit stress tolerance by integrating stom
Abstract
SUMMARY Innovative strategies are essential to enhance crop resilience against drought and heat stress intensified by climate change. Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway that improves water‐use efficiency (WUE) by shifting COfixation to the nighttime. The common ice plant () utilizes NADP‐malic enzymes (ME) for malate decarboxylation during its facultative CAM transition. In this study, we characterized the cytosolicenzyme, which is highly expressed in the ice plant under water‐deficit stress. Transgenicplants overexpressingexhibited reduced stomatal density, size, and conductance, leading to enhanced instantaneous WUE. Although these modifications resulted in reduced biomass and seed yield under low‐light conditions, the transgenic lines showed significantly improved survival and growth under both acute and chronic water‐deficit stress. Additionally,overexpression conferred improved vegetative growth under high‐light stress conditions. Notably,overexpression upregulated many genes within the flavonoid biosynthetic pathway, resulting in a marked increase in total flavonoid content. These flavonoids acted as effective antioxidants that facilitated the scavenging of reactive oxygen species (ROS), thereby reducing oxidative damage and malondialdehyde (MDA) levels under both water‐deficit and high‐light stress conditions. These results demonstrate that cytosolicis a key enzyme for conferring water‐deficit stress tolerance by integrating stomatal‐mediated water conservation with flavonoid‐driven ROS‐scavenging mechanisms. Significance Statement To sustain agricultural productivity in the face of future climate changes, innovative strategies are required to enhance crop resilience and tolerance to increasingly hot and dry conditions. Here, we report the beneficial effects of overexpression ofthat significantly improved vegetative biomass and seed production inunder water‐deficit stress conditions through decreased transpiration and increased instantaneous water‐use efficiency as well as through increased ROS‐scavenging flavonoid accumulation, thereby improving water‐deficit stress tolerance. short