FLOWERING PHENOLOGY AND SEXUAL ALLOCATION IN SINGLE-MUTATION LINEAGES OF ARABIDOPSIS THALIANA

AbstractInterspecific competition reduces resource availability and can affect evolution. We quantified multivariate selection in the presence and absence of strong interspecific competition using a greenhouse experiment with 35 natural accessions of Arabidopsis thaliana. We assessed selection on nine traits representing plant phenology, growth, and architecture, as well as their plasticities. Competition reduced biomass and fitness by over 98%, and plastic responses to competition varied by genotype (significant G × E) for all traits except specific leaf area (SLA). Competitive treatments altered selection on flowering phenology and plant architecture, with significant selection on all phenology traits and most architecture traits under competition-present conditions but little indication that selection occurred in the absence of competitors. Plasticity affected fitness only in competition-present conditions, where plasticity in flowering time and early internode lengths was adaptive. The competitive environment caused changes in the trait correlation structure and surprisingly reduced phenotypic integration, which helped explain some of the observed selection patterns. Despite this overall shift in the trait correlation matrix, genotypes with delayed flowering had lower SLA (thicker, tougher leaves) regardless of the competitive environment, a pattern we have not seen previously reported in the literature. Overall, our study highlights multiple ways in which interspecific competition can alter selective regimes, contributing to our understanding of variability in selection processes over space and time.

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Rapid hyperosmotic-induced Ca2+ responses in Arabidopsis thaliana exhibit sensory potentiation and establish involvement of plastidial KEA transporters

10.1101/048330 ◽

2016 ◽

Author(s):

Aaron B. Stephan ◽

Hans-Henning Kunz ◽

Eric Yang ◽

Julian Schroeder

Keyword(s):

Arabidopsis Thaliana ◽

Osmotic Stress ◽

Stress Responses ◽

Hyperosmotic Stress ◽

Single Mutation ◽

Water Limitation ◽

Rapid Responses ◽

Genetic Perturbations ◽

Intracellular Ca ◽

Quantitative Understanding

Abstract:Plants experience hyperosmotic stress when faced with saline soils and possibly drought stress, but it is currently unclear how plants perceive this stress in an environment of dynamic water availabilities. Hyperosmotic stress induces a rapid rise in intracellular Ca2+ concentrations ([Ca2+]i) in plants, and this Ca2+ response may reflect the activities of osmo-sensory components. Here, we find in the reference plant Arabidopsis thaliana that the rapid hyperosmotic-induced Ca2+ response exhibited enhanced response magnitudes after pre-exposure to an intermediate hyperosmotic stress. We term this phenomenon “osmo-sensory potentiation”. The initial sensing and potentiation occurred in intact plants as well as in roots. Having established a quantitative understanding of WT responses, we investigated effects of pharmacological inhibitors and candidate channel/transporter mutants. Quintuple MSL channel mutants as well as double MCA channel mutants did not affect the response. However interestingly, double mutations in the plastid KEA transporters, kea1kea2, and a single mutation that does not visibly affect chloroplast structure, kea3, impaired the rapid hyperosmotic-induced Ca2+ responses. These mutations did not significantly affect sensory potentiation of the response. These findings suggest that plastids may play an important role in the early steps mediating the response to hyperosmotic stimuli. Together, these findings demonstrate that the plant osmosensory components necessary to generate rapid osmotic-induced Ca2+ responses remains responsive under varying osmolarities, endowing plants with the ability to perceive the dynamic intensities of water limitation imposed by osmotic stress.Significance Statement:The sensitivity ranges of biological sensors determine when‐ and to what extent responses to environmental stimuli are activated. Plants may perceive water limitation imposed by soil salinity or drought in the form of osmotic stress, among other mechanisms. Rapid osmotic stress-induced Ca2+ responses provide the opportunity to quantitatively characterize the responses to osmotic stress under environmental and genetic perturbations. This report describes a phenomenon whereby prior exposure to osmotic stress increases the sensitivity of the rapid responses to subsequent stress. Further, mutations in specific plastidial transporters were found to reduce the stress response. These findings inform the reader of new avenues for understanding osmotic stress responses in plants.

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Plasma Membrane Aquaporin Members PIPs Act in Concert to Regulate Cold Acclimation and Freezing Tolerance Responses in Arabidopsis thaliana

Plant and Cell Physiology ◽

10.1093/pcp/pcaa005 ◽

2020 ◽

Vol 61 (4) ◽

pp. 787-802 ◽

Cited By ~ 2

Author(s):

Arifa Rahman ◽

Yukio Kawamura ◽

Masayoshi Maeshima ◽

Abidur Rahman ◽

Matsuo Uemura

Keyword(s):

Arabidopsis Thaliana ◽

Plasma Membrane ◽

Cold Acclimation ◽

Freezing Tolerance ◽

Cell Biology ◽

Integrated Approach ◽

Freezing Stress ◽

Single Mutation ◽

Plasma Membrane Intrinsic Proteins

Abstract Aquaporins play a major role in plant water uptake at both optimal and environmentally stressed conditions. However, the functional specificity of aquaporins under cold remains obscure. To get a better insight to the role of aquaporins in cold acclimation and freezing tolerance, we took an integrated approach of physiology, transcript profiling and cell biology in Arabidopsis thaliana. Cold acclimation resulted in specific upregulation of PIP1;4 and PIP2;5 aquaporin (plasma membrane intrinsic proteins) expression, and immunoblotting analysis confirmed the increase in amount of PIP2;5 protein and total amount of PIPs during cold acclimation, suggesting that PIP2;5 plays a major role in tackling the cold milieu. Although single mutants of pip1;4 and pip2;5 or their double mutant showed no phenotypic changes in freezing tolerance, they were more sensitive in root elongation and cell survival response under freezing stress conditions compared with the wild type. Consistently, a single mutation in either PIP1;4 or PIP2;5 altered the expression of a number of aquaporins both at the transcriptional and translational levels. Collectively, our results suggest that aquaporin members including PIP1;4 and PIP2;5 function in concert to regulate cold acclimation and freezing tolerance responses.

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Rapid hyperosmotic-induced Ca2+ responses in Arabidopsis thaliana exhibit sensory potentiation and involvement of plastidial KEA transporters

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1519555113 ◽

2016 ◽

Vol 113 (35) ◽

pp. E5242-E5249 ◽

Cited By ~ 33

Author(s):

Aaron B. Stephan ◽

Hans-Henning Kunz ◽

Eric Yang ◽

Julian I. Schroeder

Keyword(s):

Arabidopsis Thaliana ◽

Hyperosmotic Stress ◽

Saline Soils ◽

Single Mutation ◽

Wild Type ◽

Intact Plants ◽

Reference Plant ◽

Intracellular Ca ◽

Quantitative Understanding ◽

Small Conductance

Plants experience hyperosmotic stress when faced with saline soils and possibly with drought stress, but it is currently unclear how plant roots perceive this stress in an environment of dynamic water availabilities. Hyperosmotic stress induces a rapid rise in intracellular Ca2+ concentrations ([Ca2+]i) in plants, and this Ca2+ response may reflect the activities of osmo-sensory components. Here, we find in the reference plant Arabidopsis thaliana that the rapid hyperosmotic-induced Ca2+ response exhibited enhanced response magnitudes after preexposure to an intermediate hyperosmotic stress. We term this phenomenon “osmo-sensory potentiation.” The initial sensing and potentiation occurred in intact plants as well as in roots. Having established a quantitative understanding of wild-type responses, we investigated effects of pharmacological inhibitors and candidate channel/transporter mutants. Quintuple mechano-sensitive channels of small conductance-like (MSL) plasma membrane-targeted channel mutants as well as double mid1-complementing activity (MCA) channel mutants did not affect the response. Interestingly, however, double mutations in the plastid K+ exchange antiporter (KEA) transporters kea1kea2 and a single mutation that does not visibly affect chloroplast structure, kea3, impaired the rapid hyperosmotic-induced Ca2+ responses. These mutations did not significantly affect sensory potentiation of the response. These findings suggest that plastids may play an important role in early steps mediating the response to hyperosmotic stimuli. Together, these findings demonstrate that the plant osmo-sensory components necessary to generate rapid osmotic-induced Ca2+ responses remain responsive under varying osmolarities, endowing plants with the ability to perceive the dynamic intensities of water limitation imposed by osmotic stress.

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