I am a PhD student working on leaf development in tomato in the John Innes Centre (Norwich, UK).
Learn how plants deal with water stress and how we can exploit it to feed 9 billion people in 2050!
Water availability is the most limiting abiotic factor for crop productivity. As a consequence of climate change, many areas worldwide are predicted to be affected by long drought episodes, threatening food production. This, together with the exponential growth of the world population, foreseen to reach nearly 10 billion by 2050, has led plant scientists to explore and exploit the mechanisms of drought tolerance in plants.
Adaptation of their anatomy. When plants are subjected to drought, they can modify their organ architecture. Changes in the leaf surface and photosynthetic tissue have been found to improve the performance of plants under water stress. At a whole plant level, plants can allocate their resources and energy to specific organs, for example increasing the root length.
Changes at the cellular level. Drought leads to changes in the cell structures, especially affecting the cell wall, including thickness and elasticity. All these adaptations help cells maintain their water status and stay functional under stress.
Protection of photosynthesis apparatus. Drought stress leads to the production of damaging reactive oxygen species, which can affect photosynthesis and compromise plant growth. Different antioxidants can minimize this harmful effect, and many plant species have developed different metabolic pathways to increase production of this type of compounds.
Introduction of genes related to stress response. Some specific genes, especially transcription factors that can switch on or off big sets of genes, have been introduced in major crops, such as rice, wheat or tomato, achieving a high degree of drought tolerance.
Retrieval of traits from wild relatives. Many wild relatives of modern crops can grow in very hostile conditions, including arid regions where drought is commonplace. Breeding programs are now including some of these species, as wild tomato or wheat, to improve the performance of major crops.
Rediscovery of traditional cultivars. As a result of globalization and homogenization of agricultural practices, for each crop there are a series of preferred varieties that have been traditionally selected for traits such as yield. Local, drought-tolerant varieties are being rediscovered and used to improve high-yield varieties.
The combination of these different approaches will be key to ensure a food-secured planet!
Abstract: Although the root system is indispensable for absorption of nutrients and water, it is poorly studied in maize owing to the difficulties of direct measurement of roots. Here, 103 maize lines were used to compare root architectures under well-watered and water-stressed conditions. Significant genetic variation, with medium to high heritability and significant correlations, was observed for root traits. Total root length (TRL) and total root surface area (TSA) had high phenotypical diversity, and TRL was positively correlated with TSA, root volume, and root forks. The first two principal components explained 94.01% and 91.15% of total root variation in well-watered and water-stressed conditions, respectively. Thus, TRL and TSA, major contributors to root variation, can be used as favorable selection criteria at the seedling stage. We found that stiff stalk and non-stiff stalk groups (temperate backgrounds) showed relatively higher mean values for root morphological diversity than the TST group (tropical/subtropical background). Of the tested lines, 7, 42, 45, and 9 were classified as drought sensitive, moderately sensitive, moderately drought tolerant, and highly drought tolerant, respectively. Seven of the 9 extremely drought tolerant lines were from the TST group, suggesting that TST germplasms harbor valuable genetic resources for drought tolerance that could be used in breeding to improve abiotic stress tolerance in maize.
Pub.: 15 Sep '15, Pinned: 26 Apr '17
Abstract: Herbaceous species can modify leaf structure during the growing season in response to drought stress and water loss. Evolution can select combinations of traits in plants for efficient water use in restricted environments. We investigated plant traits that mediate adaptation and acclimation to water stress in two herbaceous drought‐tolerant species. Anatomical, morphological and physiological traits related to stems and leaves were examined under optimal watering (OW) and a long period of restricted watering (RW) in 11 accessions from three Solanaceae species (Solanum chilense, S. peruvianum and S. lycopersicum). The relationships between these traits were tested using linear regression and PCA. There were significant differences in anatomical traits between the species under both OW and RW, where leaf area correlated with stem diameter. Proline and total carbohydrates accumulated highly in S. chilense and S. peruvianum, respectively, and these osmolytes were strongly correlated with increased osmotic potential. Stomatal density varied between species but not between acclimation treatments, while stomatal rate was significantly higher in wild tomatoes. There was a strong positive relationship between stem growth rate and a group of traits together expressed as total stomatal number. Total stomata is described by integration of leaf area, stomatal density, height and internode length. It is proposed that constitutive adaptations and modifications through acclimation that mediate RW play an important role in tolerance to drought stress in herbaceous plants. The capacity for growth under drought stress was not associated with any single combination of traits in wild tomatoes, since the two species differed in relative levels of expression of various phenotypic traits.
Pub.: 25 Nov '15, Pinned: 26 Apr '17
Abstract: WUEi (intrinsic water use efficiency) is a complex (multi)-trait, that depends on several physiological processes, driving plant productivity and its relation with a changing environment. Climatic change predictions estimate increases in temperature and drought in the semi-arid regions, rendering improved water use efficiency is a mandatory objective to maintain the current global food supply. The aims of this review were (i) to identify through a meta-analysis the leaf traits mostly related to intrinsic water use efficiency (WUEi, the ratio between A - net photosynthesis and gs - stomatal conductance), based on a newly compiled dataset covering more than 200 species/varieties and 106 genus of C3 plants (ii) to describe the main potential targets for WUEi improvement via biotechnological manipulations and (iii) to introduce emergent and innovative technologies including UAVs (Unmanned Aerial Vehicles) to scale up levels from leaf to whole plant water status. We confirmed that increases in gm/gs and Vcmax/gs ratios are systematically related with increases in WUEi maintained across species, habitats, and environmental conditions. Other emergent opportunities to improve WUEi are described such as the relationship between photosynthesis and respiration and their link with metabolomics. Finally, we outline our hypothesis that we are observing the advent of a "smart" agriculture, wherein new technologies, such as UAVs equipped with remote sensors will rapidly facilitate an efficient water use regulating the irrigation schedule and determination, under field conditions, of cultivars with improved water use efficiency. We, therefore, conclude that the multi-disciplinary challenge toward WUE has only just begun.
Pub.: 13 Aug '14, Pinned: 26 Apr '17
Abstract: The AP2/ERF family is a plant-specific transcription factor (TF) family whose members have been associated with various developmental processes and stress tolerance. Here, we functionally characterized the drought-inducible OsERF48, a group Ib member of the rice ERF family with four conserved motifs, CMI-1, -2, -3 and -4. A transactivation assay in yeast revealed that the C-terminal CMI-1 motif was essential for OsERF48 transcriptional activity. When OsERF48 was overexpressed in an either a root-specific (ROX(OsERF48) ) or whole-body (OX(OsERF48) ) manner, transgenic plants showed a longer and denser root phenotype compared to the nontransgenic (NT) controls. When plants were grown on a 40% polyethylene glycol (PEG)-infused medium under in vitro drought conditions, ROX(OsERF48) plants showed a more vigorous root growth than OX(OsERF48) and NT plants. In addition, the ROX(OsERF48) plants exhibited higher grain yield than OX(OsERF48) and NT plants under field-drought conditions. We constructed a putative OsERF48 regulatory network by cross-referencing ROX(OsERF48) root-specific RNA-seq data with a co-expression network database, from which we inferred the involvement of 20 drought-related genes in OsERF48-mediated responses. These included genes annotated as being involved in stress signaling, carbohydrate metabolism, cell-wall proteins, and drought-responses. They included, OsCML16, a key gene in calcium signaling during abiotic stress, which was shown to be a direct target of OsERF48 by Chromatin Immunoprecipitation (ChIP)-qPCR analysis and a transient protoplast expression assay. Our results demonstrated that OsERF48 regulates OsCML16, a calmodulin-like protein gene that enhance root growth and drought tolerance. This article is protected by copyright. All rights reserved.
Pub.: 01 Mar '17, Pinned: 26 Apr '17
Abstract: Low water availability is the major environmental factor limiting crop productivity. Transcriptome analysis was used to study terminal drought response in wild emmer wheat, Triticum dicoccoides, genotypes contrasting in their productivity and yield stability under drought stress. A total of 5,892 differentially regulated transcripts were identified between drought and well-watered control and/or between drought resistant (R) and drought susceptible (S) genotypes. Functional enrichment analyses revealed that multilevel regulatory and signalling processes were significantly enriched among the drought-induced transcripts, in particular in the R genotype. Therefore, further analyses were focused on selected 221 uniquely expressed or highly abundant transcripts in the R genotype, as potential candidates for drought resistance genes. Annotation of the 221 genes revealed that 26% of them are involved in multilevel regulation, including: transcriptional regulation, RNA binding, kinase activity and calcium and abscisic acid signalling implicated in stomatal closure. Differential expression patterns were also identified in genes known to be involved in drought adaptation pathways, such as: cell wall adjustment, cuticular wax deposition, lignification, osmoregulation, redox homeostasis, dehydration protection and drought-induced senescence. These results demonstrate the potential of wild emmer wheat as a source for candidate genes for improving drought resistance.
Pub.: 25 Mar '10, Pinned: 26 Apr '17
Abstract: Although domesticated tomato is cultivated by wild tomato, there are a lot of differences between cultivated tomato and wild tomato, such as shape, physiological function and life history. Many studies show that wild tomato has better salt resistance and drought resistance. In addition to, domesticated tomato's fruit is bigger and has more nutritious than wild tomato. The different features are closely related to differentially expressed genes. We identified 126 up-regulated differentially expressed genes and 87 down-regulated differentially expressed genes in cultivated tomato and wild tomato by RNA-Seq. These differentially expressed genes may be associated with salt resistance, drought resistance and fruit nutrition. These differentially expressed genes also further highlight the large-scale reconstruction between wild and cultivated species. In this paper, we mainly study GO enrichment analysis and pathway analysis of the differentially expressed genes. After GO and pathway enrichment analysis, a set of significantly enriched GO annotations and pathways were identified for the differentially expressed genes. What's more, we also identified long non-coding RNAs and mRNAs in the two species and analyzed its essential features. In addition to, we construct a co-expression network of long non-coding RNAs and mRNAs, and annotate mRNAs associated with long non-coding RNAs as target genes, and speculate the regulation function of long non-coding RNAs. In total, our results reveal the effects of artificial and natural selection on tomato's transcript, providing scientific basis for tomato's research in the future.
Pub.: 10 Mar '17, Pinned: 26 Apr '17
Abstract: Flavonoids, as plant secondary metabolites, are widespread throughout the plant kingdom and involved in many physiological and biochemical processes. Drought resistance is attributed to flavonoids with respect to protective functions in the cell wall and membranes. The flavanone 3-hydroxylase (F3H) gene which encodes flavanone 3-hydroxylase, is essential in flavonoids biosynthetic pathway. Lycium chinense (L. chinense) is a deciduous woody perennial halophyte that grows under a large variety of environmental conditions and survives under extreme drought stress. A novel cDNA sequence coding a F3H gene in Lycium chinense (LcF3H, GenBank: KJ636468.1) was isolated. The open reading frame of LcF3H comprised 1101 bp encoding a polypeptide of 366 amino acids with a molecular weight of about 42 kDa and an isoelectric point of 5.32. The deduced LcF3H protein showed high identities with other plant F3Hs, and the conserved motifs were found in LcF3H at similar positions like other F3Hs. The recombinant protein converted naringen into dihydrokaempferol in vitro. Since studies have shown that amongst flavonoids, flavan-3-ols (catechin and epicatechin) have direct free radical scavenging activity to maintain the normal physiological function of cells in vivo, these data support the possible relationship between the oxidative damage and the regulation of LcF3H gene expression in L. chinense under drought stress. In order to better understand the biotechnological potential of LcF3H, gene overexpression was conducted in tobacco. The content of flavan-3-ols and the tolerance to drought stress were increased in LcF3H overexpressing tobacco. Analysis of transgenic tobacco lines also showed that antioxidant enzyme activities were increased meanwhile the malondialdehyde (MDA) content and the content of H2O2 were reduced comparing to nontransformed tobacco plants. Furthermore, the photosynthesis rate was less decreased in the transgenetic plants. These results suggest that LcF3H plays a role in enhancing drought tolerance in L. chinense, and its overexpression increases tolerance to drought stress by improving the antioxidant system in tobacco.
Pub.: 10 Dec '15, Pinned: 26 Apr '17
Abstract: Plant responses to drought stress require the regulation of transcriptional networks via drought responsive transcription factors, which mediate a range of morphological and physiological changes. AP2/ERF transcription factors are known to act as key regulators of drought resistance transcriptional networks; however, little is known about the associated molecular mechanisms that give rise to specific morphological and physiological adaptations. In this study, we functionally characterized the rice (Oryza sativa) drought responsive AP2/ERF transcription factor, OsERF71, which is predominantly expressed in the root meristem, pericycle, and endodermis. Overexpression of OsERF71 either throughout the entire plant or specifically in roots, resulted in a drought resistance phenotype at the vegetative growth stage, indicating that overexpression in roots was sufficient to confer drought resistance. The root specific overexpression was more effective in conferring drought resistance at the reproductive stage, such that grain yield was increased by 23-42% over wild type plants or whole-body overexpressing transgenic lines under drought conditions. OsERF71 overexpression in roots elevated the expression levels of genes related to cell wall loosening and lignin biosynthetic genes, which correlated with changes in root structure, the formation of enlarged aerenchyma and high lignification levels. Furthermore, OsERF71 was found to directly bind to the promoter of OsCCR1, a key gene in lignin biosynthesis. These results indicate that the OsERF71-mediated drought resistance pathway recruits factors involved in cell wall modification to enable root morphological adaptations, thereby providing a mechanism for enhancing drought resistance.
Pub.: 07 Jul '16, Pinned: 26 Apr '17