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bia  cam  drought  expression  input agroecosystems  metabolic  phenotypes  plants  reduced  root phenotypes  root  stress  water deficit  water 
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Preview: Journal of Experimental Botany - Advance Access

Journal of Experimental Botany Advance Access





Published: Sat, 17 Feb 2018 00:00:00 GMT

Last Build Date: Fri, 16 Feb 2018 20:49:03 GMT

 



Rightsizing Root Phenotypes for Drought resistance

Sat, 17 Feb 2018 00:00:00 GMT

Abstract
I propose that reduced root development would be advantageous for drought resistance in high-input agroecosystems. Selection regimes for crop ancestors and landraces include multiple stresses, intense competition, and variable resource distribution, which favored prolific root production, developmental plasticity in response to resource availability, and maintenance of unspecialized root tissues. High-input agroecosystems have removed many of these constraints to root function. Therefore, root phenotypes that focus on water capture at the expense of ancestral adaptations would be better suited to high-input agroecosystems. Parsimonious architectural phenotypes include fewer axial roots, reduced density of lateral roots, reduced growth responsiveness to local resource availability, and greater loss of roots that do not contribute to water capture. Parsimonious anatomical phenotypes include reduced number of cortical cell files, greater loss of cortical parenchyma to aerenchyma and senescence, and larger cortical cell size. Parsimonious root phenotypes may be less useful in low-input agroecosystems, which are characterized by multiple challenges and tradeoffs for root function in addition to water capture. Analysis of the fitness landscape of root phenotypes is a complex challenge that will be aided by the development of robust functional-structural models capable of simulating the dynamics of root-soil interactions.



Blue light-dependent changes in loosely bound calcium in Arabidopsis mesophyll cells: an X-ray microanalysis study

Thu, 15 Feb 2018 00:00:00 GMT

Journal of Experimental Botany, Vol. 67, No. 13 pp. 3953–3964, 2016 doi: 10.1093/jxb/erw089



Dynamics of Metabolic Responses to Combined Heat and Drought Spells in Arabidopsis Thaliana under Ambient and Rising Atmospheric CO2

Thu, 15 Feb 2018 00:00:00 GMT

Abstract
As a consequence of global change processes, plants will be increasingly challenged by extreme climatic events, against a background of elevated atmospheric CO2. We analysed responses of Arabidopsis thaliana to a combination of heat wave and water deficit at ambient and elevated CO2, and provided mechanistic insight on changes in primary metabolism. Climate extreme-induced metabolic changes are dynamic and molecule class-specific. Concentrations of soluble sugars and amino acids increased transiently after short (4 d) exposure to heat and drought, and readjusted to control levels under prolonged (8 d) stress. In contrast, fatty acids showed persistent changes during the stress period. Elevated CO2 reduced the stress impact on sugar and amino acid metabolism, but not on fatty acids. Integrating metabolite data with transcriptome results, revealed that some of the metabolic changes are regulated at the transcriptional level. Multivariate analyses grouped metabolites on the basis of stress exposure time, indicating specificity in metabolic responses to short and prolonged stress. Taken together, the results indicate that dynamic metabolic reprograming plays an important role in plant acclimation to climatic extremes. The extent of such metabolic adjustments is less under high CO2, further pointing towards the role of high CO2 in stress mitigation.



NH4+ intensifies CAM photosynthesis and counteracts drought effects in Guzmania monostachia by increasing malate transport and antioxidant capacity

Thu, 15 Feb 2018 00:00:00 GMT

Abstract
Guzmania monostachia (Bromeliaceae) is a tropical epiphyte capable of upregulating crassulacean acid metabolism (CAM) in its photosynthetic tissues in response to changing nutrient and water availability. Previous studies have shown that under drought there is a gradient of increasing CAM expression from the basal (youngest) to apical (oldest) portion of the leaves, and additionally that nitrogen deficiency can further increase CAM intensity in the leaf apex of this bromeliad. The present study investigated the interrelationships between nitrogen source (nitrate and/or ammonium) and water deficit in regulating CAM expression in G. monostachia leaves. Highest CAM activity was observed under ammonium nutrition in combination with water deficit. This was associated with enhanced activity of the key enzyme phosphoenolpyruvate carboxylase, elevated rates of ATP- and PPi-dependent proton transport at the vacuolar membrane in the presence of malate, and increased transcript levels of the vacuolar malate channel, ALMT. Water deficit was consistently associated with higher levels of total soluble sugars, which were maximal under ammonium nutrition, as were the activities of several antioxidant enzymes (SOD, CAT, APX and GR). Thus, ammonium nutrition, whilst associated with the highest degree of CAM induction in G. monostachia, also mitigates the effects of water deficit by osmotic adjustment and can limit oxidative damage in the leaves of this bromeliad under conditions that may be typical of its epiphytic habitat.



Arabidopsis BRASSINOSTEROID INACTIVATOR2 is a typical BAHD acyltransferase involved in brassinosteroid homeostasis

Thu, 15 Feb 2018 00:00:00 GMT

Abstract
Brassinosteroids (BRs) are plant-specific steroidal hormones, the homeostasis of which is crucial for various aspects of plant growth and development. However, to date, the BR inactivation process has not been thoroughly elucidated. In this study, we identified and characterized a novel BAHD family acyltransferase gene, BRASSINOSTEROID INACTIVATOR2 (BIA2), involved in BR inactivation. Plants overexpressing BIA2 displayed typical BR-deficient phenotypes, which were rescued by exogenous BR treatment. Real-time qRT-PCR and transcriptome analyses showed that virtually all of the BR-biosynthetic gene expression levels were increased, whereas the expression of many BR- inactivation genes was reduced in OE-BIA2 plants. Root inhibition assays showed that the root growth of OE-BIA2 plants was inhibited. We obtained plants with an intermediate phenotype by crossing the OE-BIA2 plants with OE-BRASSINOSTEROID-INSENSITIVE1 (BRI1) plants. The null BIA2 mutants had longer hypocotyls in the dark. BIA2 was predominantly expressed in roots, and its expression was induced by 24-epiBL or dark treatment but exhibited a differential expression pattern compared with its homologue BIA1. Furthermore, genetic transformation with point mutant and deleted BIA2 constructs confirmed that the HXXXD motif is essential for the function of BIA2. Taken together, these findings indicate that BIA2 is a typical BAHD acyltransferase that is involved in BR homeostasis, which may inactivate bioactive BRs by esterification, particularly in roots and hypocotyls under dark condition.