Abstract
Simple SummaryWater scarcity is one of the main threats for the future of agriculture and the worldwide population. Improving the ability of crop species to grow and survive with less water is therefore essential. A fundamental goal of most scientists working in this area is to understand the mechanisms plants must potentiate to better survive under reduced water availability. Here we provide evidence that accumulation of anthocyanins, a major player in red leaf color, may fulfil two important functions. First, they serve as a filter for protecting plants against excessive sunlight; second, they control plant water loss by reducing stomatal transpiration and density. Since excessive sunlight and temperature, associated with climate change, come along with water shortage, these pigments may protect and help plants to survive throughout hot and dry seasons. Our results have important social implications for people living in areas where rising temperatures and water shortages are already critical. Breeding programs to obtain crops with these stress tolerance traits can be specifically designed for these environments.Abiotic stresses will be one of the major challenges for worldwide food supply in the near future. Therefore, it is important to understand the physiological mechanisms that mediate plant responses to abiotic stresses. When subjected to UV, salinity or drought stress, plants accumulate specialized metabolites that are often correlated with their ability to cope with the stress. Among them, anthocyanins are the most studied intermediates of the phenylpropanoid pathway. However, their role in plant response to abiotic stresses is still under discussion. To better understand the effects of anthocyanins on plant physiology and morphogenesis, and their implications on drought stress tolerance, we used transgenic tobacco plants (AN1), which over-accumulated anthocyanins in all tissues. AN1 plants showed an altered phenotype in terms of leaf gas exchanges, leaf morphology, anatomy and metabolic profile, which conferred them with a higher drought tolerance compared to the wild-type plants. These results provide important insights for understanding the functional reason for anthocyanin accumulation in plants under stress.
Highlights
Introduction distributed under the terms andAbiotic stresses are a major constraint for crop productivity worldwide [1,2] and exacerbate yield loss under climate change [3]
Proline, ornithine, arginine, aspartic acid, glutamine, glycine, isoleucine, monoethanolamine (MEA) and tyrosine concentrations were significantly higher in AN1 compared to WT plants, while no statistically significant difference was observed for the other amino acids (Table 1)
Experimental evidence reported in this paper indicates that the interaction between anthocyanins and light produces a stress-resistant phenotype thanks to the induction of morpho-physiological modifications able to facilitate plant adaptation to water scarcity
Summary
Introduction distributed under the terms andAbiotic stresses are a major constraint for crop productivity worldwide [1,2] and exacerbate yield loss under climate change [3]. The biosynthetic pathways of these specialized metabolites are highly conserved in the plant kingdom, which has probably played a key role in their adaptation to environmental stresses throughout evolution [10]. Anthocyanins are compounds with potential significance in plant stress response. The main roles attributed to anthocyanins in mediating responses to stress are linked with their antioxidant [17,18] and light-screening properties [12,19,20,21]. While there is convincing experimental evidence that confirms an anthocyanin light-screening activity [19,20,22,23], the actual contribution of these molecules to the plant antioxidant machinery during environmental stresses is still under debate [11,12,24]. The proposed roles (light-screening and antioxidant activities) do not necessary exclude each other, doubts regarding the anthocyanin antioxidant activity are based on their vacuolar localization, which is spatially far from the primary sites of reactive oxygen species (ROS)
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