Shade tolerance: when growing tall is not an option
TL;DR: It is argued that molecular approaches using model and non-model species should help identify the molecular pathways that underpin shade tolerance, thus providing knowledge for further crop improvement.
About: This article is published in Trends in Plant Science.The article was published on 2013-02-01. It has received 302 citations till now. The article focuses on the topics: Shade tolerance & Shade avoidance.
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TL;DR: In describing well-established links between light perception and hormonal changes, this review discusses examples of light-regulated processes throughout a plant's life cycle for which it is known how light signals lead to hormonal regulation.
Abstract: Light is crucial for plant life, and perception of the light environment dictates plant growth, morphology, and developmental changes. Such adjustments in growth and development in response to light conditions are often established through changes in hormone levels and signaling. This review discusses examples of light-regulated processes throughout a plant's life cycle for which it is known how light signals lead to hormonal regulation. Light acts as an important developmental switch in germination, photomorphogenesis, and transition to flowering, and light cues are essential to ensure light capture through architectural changes during phototropism and the shade avoidance response. In describing well-established links between light perception and hormonal changes, we aim to give insight into the mechanisms that enable plants to thrive in variable light environments.
262 citations
Cites background from "Shade tolerance: when growing tall ..."
...Many hormones play a role in the events leading from low-R:FR perception to shade avoidance– related architectural changes, including GA, ET, auxin, brassinosteroid, cytokinin, and jasmonic acid (12, 14, 46, 73, 92)....
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TL;DR: This synthesis provides a strong quantitative basis for understanding plant acclimation to light, from molecular to whole plant responses, but also identifies the variables that currently form weak spots in knowledge, such as respiration and reproductive characteristics.
Abstract: By means of meta-analyses we determined how 70 traits related to plant anatomy, morphology, chemistry, physiology, growth and reproduction are affected by daily light integral (DLI; mol photons m-2 d-1 ). A large database including 500 experiments with 760 plant species enabled us to determine generalized dose-response curves. Many traits increase with DLI in a saturating fashion. Some showed a more than 10-fold increase over the DLI range of 1-50 mol m-2 d-1 , such as the number of seeds produced per plant and the actual rate of photosynthesis. Strong decreases with DLI (up to three-fold) were observed for leaf area ratio and leaf payback time. Plasticity differences among species groups were generally small compared with the overall responses to DLI. However, for a number of traits, including photosynthetic capacity and realized growth, we found woody and shade-tolerant species to have lower plasticity. We further conclude that the direction and degree of trait changes adheres with responses to plant density and to vertical light gradients within plant canopies. This synthesis provides a strong quantitative basis for understanding plant acclimation to light, from molecular to whole plant responses, but also identifies the variables that currently form weak spots in our knowledge, such as respiration and reproductive characteristics.
247 citations
TL;DR: It is hypothesize that drought stress enhances insect resistance due to synergistic interactions between JA and ABA signaling, and likely reduces plant resistance to chewing herbivores due to its negative cross-talk with JA.
Abstract: Adaptive plant responses to specific abiotic stresses or biotic agents are fine-tuned by a network of hormonal signaling cascades, including abscisic acid (ABA), ethylene, jasmonic acid (JA) and salicylic acid. Moreover, hormonal cross-talk modulates plant responses to abiotic stresses and defenses against insect herbivores when they occur simultaneously. How such interactions affect plant responses under multiple stresses, however, is less understood, even though this may frequently occur in natural environments. Here, we review our current knowledge on how hormonal signaling regulates abiotic stress responses and defenses against insects, and discuss the few recent studies that attempted to dissect hormonal interactions occurring under simultaneous abiotic stress and herbivory. Based on this we hypothesize that drought stress enhances insect resistance due to synergistic interactions between JA and ABA signaling. Responses to flooding or waterlogging involve ethylene signaling, which likely reduces plant resistance to chewing herbivores due to its negative cross-talk with JA. However, the outcome of interactions between biotic and abiotic stress signaling is often plant and/or insect species-dependent and cannot simply be predicted based on general knowledge on the involvement of signaling pathways in single stress responses. More experimental data on non-model plant and insect species are needed to reveal general patterns and better understand the molecular mechanisms allowing plants to optimize their responses in complex environments.
242 citations
Cites background from "Shade tolerance: when growing tall ..."
...Similarly, BRs, AUXs and CKs influence JA sig- naling both positively and negatively in regulating responses to herbivores (Dervinis et al. 2010; Yang et al. 2011; Meldau et al. 2011)....
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...Growth hormones in defense regulation Recently, phytohormones such as gibberellins (GAs), brassinosteroids (BRs), auxins (AUXs) and cytokinins (CKs) have also been shown to modulate JA-mediated responses to herbivores (Figs....
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...AUXs and JA, however, synergis- tically constrain N. attenuata regrowth after M. sexta herbivory (Shi et al. 2006; Onkokesung et al. 2010b; Noir et al. 2013; Machado et al. 2013)....
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...Stomatal opening, on the other hand, is pro- moted by CKs and AUXs, while leaf senescence is inhib- ited by GAs, CKs and AUXs (Daszkowska-Golec and Szarejko 2013; Jibran et al. 2013)....
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...Furthermore, JA in concert with ET repress cell cycle processes and expansion of leaf cells by suppressing the cell expansion enhancers, AUXs....
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TL;DR: Current models of phytochrome function connecting light-induced conformational changes to physiological outputs are reviewed, to highlight open questions for future research and compare and contrast phy tochrome responses and signaling mechanisms among land plants.
Abstract: Phytochromes are bilin-binding photosensory receptors which control development over a broad range of environmental conditions and throughout the whole plant life cycle. Light-induced conformational changes enable phytochromes to interact with signaling partners, in particular transcription factors or proteins that regulate them, resulting in large-scale transcriptional reprograming. Phytochromes also regulate promoter usage, mRNA splicing and translation through less defined routes. In this review we summarize our current understanding of plant phytochrome signaling, emphasizing recent work performed in Arabidopsis. We compare and contrast phytochrome responses and signaling mechanisms among land plants and highlight open questions in phytochrome research.
215 citations
TL;DR: A case is made for a whole-plant, ecophysiology approach to identify the relative importance of the various neighbour detection cues and their possible interactions in determining plant performance during competition.
Abstract: Plants compete with neighbouring vegetation for limited resources. In competition for light, plants adjust their architecture to bring the leaves higher in the vegetation where more light is available than in the lower strata. These architectural responses include accelerated elongation of the hypocotyl, internodes and petioles, upward leaf movement (hyponasty), and reduced shoot branching and are collectively referred to as the shade avoidance syndrome. This review discusses various cues that plants use to detect the presence and proximity of neighbouring competitors and respond to with the shade avoidance syndrome. These cues include light quality and quantity signals, mechanical stimulation, and plant-emitted volatile chemicals. We will outline current knowledge about each of these signals individually and discuss their possible interactions. In conclusion, we will make a case for a whole-plant, ecophysiology approach to identify the relative importance of the various neighbour detection cues and their possible interactions in determining plant performance during competition.
178 citations
Cites background from "Shade tolerance: when growing tall ..."
...These elongation responses have been studied intensively and appear to rely on the combined action of a number of plant hormones, including gibberellin, auxin, brassinosteroids, and ethylene (reviewed in Jaillais and Chory, 2010; Stamm and Kumar, 2010; Gommers et al., 2013)....
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References
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TL;DR: Genevestigator as mentioned in this paper is a web-browser interface for gene expression analysis using Affymetrix GeneChip data, which allows users to retrieve the expression patterns of individual genes throughout chosen environmental conditions, growth stages, or organs.
Abstract: High-throughput gene expression analysis has become a frequent and powerful research tool in biology. At present, however, few software applications have been developed for biologists to query large microarray gene expression databases using a Web-browser interface. We present GENEVESTIGATOR, a database and Web-browser data mining interface for Affymetrix GeneChip data. Users can query the database to retrieve the expression patterns of individual genes throughout chosen environmental conditions, growth stages, or organs. Reversely, mining tools allow users to identify genes specifically expressed during selected stresses, growth stages, or in particular organs. Using GENEVESTIGATOR, the gene expression profiles of more than 22,000 Arabidopsis genes can be obtained, including those of 10,600 currently uncharacterized genes. The objective of this software application is to direct gene functional discovery and design of new experiments by providing plant biologists with contextual information on the expression of genes. The database and analysis toolbox is available as a community resource at https://www.genevestigator.ethz.ch.
2,485 citations
TL;DR: Adaptation to irradiance level is explored, focusing on traits whose significance would be elusive if considered in terms of their impact at the leaf level alone, and three energetic tradeoffs likely to shape such adaptation are outlined, involving the economics of gas exchange, support, and biotic interactions.
Abstract: Whole-plant energy capture depends not only on the photosynthetic response of individual leaves, but also on their integration into an effective canopy, and on the costs of producing and maintaining their photosynthetic capacity. This paper explores adaptation to irradiance level in this context, focusing on traits whose significance would be elusive if considered in terms of their impact at the leaf level alone. I review traditional approaches used to demonstrate or suggest adaptation to irradiance level, and outline three energetic tradeoffs likely to shape such adaptation, involving the economics of gas exchange, support, and biotic interactions. Recent models using these tradeoffs to account for trends in leaf nitrogen content, stornatal conductance, phyllotaxis, and defensive allocations in sun v. shade are evaluated. A re-evaluation of the classic study of acclimation of the photosynthetic light response in Atriplex, crucial to interpreting adaptation to irradiance in many traits, shows that it does not completely support the central dogma of adaptation to sun v. shade unless the results are analysed in terms of whole-plant energy capture. Calculations for Liriodendron show that the traditional light compensation point has little meaning for net carbon gain, and that the effective compensation point is profoundly influenced by the costs of night leaf respiration, leaf construction, and the construction of associated support and root tissue. The costs of support tissue are especially important, raising the effective compensation point by 140 pmol m- s - ' in trees 1 m tall, and by nearly 1350 pmol m - s - ' in trees 30 m tall. Effective compensation points give maximum tree heights as a function of irradiance, and shade tolerance as a function of tree height; calculations of maximum permissible height in Liriodendron correspond roughly with the height of the tallest known individual. Finally, new models for the evolution of canopy width/height ratio in response to irradiance and coverage within a tree stratum, and for the evolution of mottled leaves as a defensive measure in understory herbs, are outlined.
1,712 citations
TL;DR: This study demonstrates the feasibility of GWA studies in A. thaliana and suggests that the approach will be appropriate for many other organisms, particularly when inbred lines are available.
Abstract: Although pioneered by human geneticists as a potential solution to the challenging problem of finding the genetic basis of common human diseases, genome-wide association (GWA) studies have, owing to advances in genotyping and sequencing technology, become an obvious general approach for studying the genetics of natural variation and traits of agricultural importance. They are particularly useful when inbred lines are available, because once these lines have been genotyped they can be phenotyped multiple times, making it possible (as well as extremely cost effective) to study many different traits in many different environments, while replicating the phenotypic measurements to reduce environmental noise. Here we demonstrate the power of this approach by carrying out a GWA study of 107 phenotypes in Arabidopsis thaliana, a widely distributed, predominantly self-fertilizing model plant known to harbour considerable genetic variation for many adaptively important traits. Our results are dramatically different from those of human GWA studies, in that we identify many common alleles of major effect, but they are also, in many cases, harder to interpret because confounding by complex genetics and population structure make it difficult to distinguish true associations from false. However, a-priori candidates are significantly over-represented among these associations as well, making many of them excellent candidates for follow-up experiments. Our study demonstrates the feasibility of GWA studies in A. thaliana and suggests that the approach will be appropriate for many other organisms.
1,525 citations
TL;DR: The identification of a cluster of three genes at the Sub1 locus, encoding putative ethylene response factors, indicates that Sub1A-1 is a primary determinant of submergence tolerance in O. sativa ssp.
Abstract: Most Oryza sativa cultivars die within a week of complete submergence--a major constraint to rice production in south and southeast Asia that causes annual losses of over US 1 billion dollars and affects disproportionately the poorest farmers in the world. A few cultivars, such as the O. sativa ssp. indica cultivar FR13A, are highly tolerant and survive up to two weeks of complete submergence owing to a major quantitative trait locus designated Submergence 1 (Sub1) near the centromere of chromosome 9 (refs 3, 4, 5-6). Here we describe the identification of a cluster of three genes at the Sub1 locus, encoding putative ethylene response factors. Two of these genes, Sub1B and Sub1C, are invariably present in the Sub1 region of all rice accessions analysed. In contrast, the presence of Sub1A is variable. A survey identified two alleles within those indica varieties that possess this gene: a tolerance-specific allele named Sub1A-1 and an intolerance-specific allele named Sub1A-2. Overexpression of Sub1A-1 in a submergence-intolerant O. sativa ssp. japonica conferred enhanced tolerance to the plants, downregulation of Sub1C and upregulation of Alcohol dehydrogenase 1 (Adh1), indicating that Sub1A-1 is a primary determinant of submergence tolerance. The FR13A Sub1 locus was introgressed into a widely grown Asian rice cultivar using marker-assisted selection. The new variety maintains the high yield and other agronomic properties of the recurrent parent and is tolerant to submergence. Cultivation of this variety is expected to provide protection against damaging floods and increase crop security for farmers.
1,371 citations
TL;DR: This exploration of natural variation in strategies that improve O(2) and carbohydrate status during flooding provides valuable resources for the improvement of crop endurance of an environmental adversity that is enhanced by global warming.
Abstract: Flooding is an environmental stress for many natural and man-made ecosystems worldwide. Genetic diversity in the plant response to flooding includes alterations in architecture, metabolism, and elongation growth associated with a low O2 escape strategy and an antithetical quiescence scheme that allows endurance of prolonged submergence. Flooding is frequently accompanied with a reduction of cellular O2 content that is particularly severe when photosynthesis is limited or absent. This necessitates the production of ATP and regeneration of NAD+ through anaerobic respiration. The examination of gene regulation and function in model systems provides insight into low-O2-sensing mechanisms and metabolic adjustments associated with controlled use of carbohydrate and ATP. At the developmental level, plants can escape the low-O2 stress caused by flooding through multifaceted alterations in cellular and organ structure that promote access to and diffusion of O2. These processes are driven by phytohormones, includin...
1,337 citations