The plant hormone jasmonate (JA) controls diverse aspects of plant immunity, growth, and development. The amplitude and duration of JA responses are controlled in large part by the intracellular level of jasmonoyl-l-isoleucine (JA-Ile). In contrast to detailed knowledge of the JA-Ile biosynthetic pathway, little is known about enzymes involved in JA-Ile metabolism and turnover. Cytochromes P450 (CYP) 94B3 and 94C1 were recently shown to sequentially oxidize JA-Ile to hydroxy (12OH-JA-Ile) and dicarboxy (12COOH-JA-Ile) derivatives. Here, we report that a third member (CYP94B1) of the CYP94 family also participates in oxidative turnover of JA-Ile in Arabidopsis. In vitro studies showed that recombinant CYP94B1 converts JA-Ile to 12OH-JA-Ile and lesser amounts of 12COOH-JA-Ile. Consistent with this finding, metabolic and physiological characterization of CYP94B1 loss-of-function and overexpressing plants demonstrated that CYP94B1 and CYP94B3 coordinately govern the majority (>95%) of 12-hydroxylation of JA-Ile in wounded leaves. Analysis of CYP94-promoter-GUS reporter lines indicated that CYP94B1 and CYP94B3 serve unique and overlapping spatio-temporal roles in JA-Ile homeostasis. Subcellular localization studies showed that CYP94s involved in conversion of JA-Ile to 12COOH-JA-Ile reside on endoplasmic reticulum (ER). In vitro studies further showed that 12COOH-JA-Ile, unlike JA-Ile, fails to promote assembly of COI1-JAZ co-receptor complexes. The double loss-of-function mutant of CYP94B3 and ILL6, a JA-Ile amidohydrolase, displayed a JA profile consistent with the collaborative action of the oxidative and the hydrolytic pathways in JA-Ile turnover. Collectively, our results provide an integrated view of how multiple ER-localized CYP94 and JA amidohydrolase enzymes attenuate JA signaling during stress responses. 相似文献
Abstract: We examined the ability of developing cere-bellar cell cultures to synthesize a 71,000 MW stress protein (SP71) in response to heat shock and Cd2+ treatment. The induction of SP71 synthesis appeared to be dependent on both the age of the culture and the stressor used. Heat shock induced SP71 synthesis in freshly prepared cells and in cell cultures at each age examined, whereas Cd2+ was effective only in cultures at 7 days of age and older. These findings are discussed with reference to the development of various cell types in these cultures. 相似文献
The effects of moderate light at chilling temperature on the photosynthesis of unhardened (acclimated to +18° C) and hardened (cold-acclimated) spinach (Spinacea oleracea L.) leaves were studied by means of fluorescence-induction measurements at 20° C and 77K and by determination of quantum yield of O2 evolution. Exposure to 550 mol photons·m-2·s-1 at +4° C induced a strong photoinhibition in the unhardened leaves within a few hours. Photoinhibition manifested by a decline in quantum yield was characterized by an increase in initial fluorescence (Fo) and a decrease in variable fluorescence (Fv) and in the ratio of variable to maximum fluorescence (FV/FM), both at 77K and 20° C. The decline in quantum yield was more closely related to the decrease in the FV/FM ratio measured at 20° C, as compared with FV/FM at 77K. Quenching of the variable fluorescence of photosystem II was accompanied by a decline in photosystem-I fluorescence at 77K, indicating increased thermal de-excitation of pigments as the main consequence of the light treatment. All these changes detected in fluorescence parameters as well as in the quantum yield of O2 evolution were fully reversible within 1–3 h at a higher temperature in low light. The fast recovery led us to the view that this photoinhibition represents a regulatory mechanism protecting the photosynthetic apparatus from the adverse effects of excess light by increasing thermal energy dissipation. Long-term cold acclimation probably enforces other protective mechanisms, as the hardened leaves were insensitive to the same light treatment that induced strong inhibition of photosynthesis in unhardened leaves.Abbreviations
F0
initial fluorescence
-
FM
maximum fluorescence
-
FV
variable fluorescence (FM-F0
- PFD
photon flux density
- PS
photosystem 相似文献
1. 1. The effects of sudden changes by increasing or decreasing the measurement temperature on the oxygen consumption of the brains of Bufo arenarum and Leptodactylus ocellatus were determined.
2. 2. The experiments were carried at in vitro at temperatures which range from 4 to 37°C. The brain was oxygenated and stabilized for 20 min at each of the temperatures to which it was subjected before oxygen consumption measurements were made.
3. 3. A theoretical curve representing the variation of oxygen consumption with temperature was calculated according to the following exponential relationship; for Leptodactylus ocellatusy = 0.408 × 1.07x and for Bufo arenarumy = 0.389 × 1.065x.
4. 4. These results were compared with the brain oxygen consumption of animals acclimated to different temperatures, whose oxygen consumption was measured at a fixed temperature. Only Leptodactylus ocellatus had a significantly lower oxygen consumption in a high range of temperatures, indicating thermal compensation, probably to save metabolic reserves.
5. 5. No deterioration of the brain tissue was observed, as several passages from high to low temperatures in the range of 20°–30°C, showed a reversible oxygen consumption in acclimated and non-acclimated Bufo arenarum and Leptodactylus ocellatus.
We studied developmental and environmental constraints on leaf dynamics, morphology and physiology in the monopodial tropical palm of the Atlantic Forest biome, Euterpe edulis. Plastic responses to light environments in terms of photosynthesis, leaf size, leaf life span, patterns of biomass allocation and growth were analysed. Plants were grown during 14 months in a shade house under four different growth irradiances. Plants of Euterpe edulis were able to adjust leaf demography and biomass allocation in the different light treatments. Leaf life span increased by 100 days with decreasing light levels while the rate of leaf production decreased, consistent with lower electron transport rates. At low light levels, adjustments in biomass allocation to leaf components allowed E. edulis to reduce self-shading and increase light interception. At high light plants allocated more biomass to roots, and the plants exhibited small leaf sizes when leaves were compared using an explicit ontogenetic analysis. Ontogeny constrained the maximum size that each consecutive leaf could achieve, while growth irradiance determined the rate of leaf production and other leaf traits. Consequently, there were both, developmental constraints and environmental determinants influencing leaf demography and morphology in E. edulis. The findings of this ecophysiological and demographic study are relevant to palms growing under natural conditions and help to explain the success of E. edulis in the forest understory and its absence from large gap openings. Our results not only confirm that E. edulis is a shade tolerant species, but also show that palms are able to acclimate to different growing condition as well as trees. 相似文献
We investigated how the legacy of warming and summer drought affected microbial communities in five different replicated long‐term (>10 years) field experiments across Europe (EU‐FP7 INCREASE infrastructure). To focus explicitly on legacy effects (i.e., indirect rather than direct effects of the environmental factors), we measured microbial variables under the same moisture and temperature in a brief screening, and following a pre‐incubation at stable conditions. Specifically, we investigated the size and composition of the soil microbial community (PLFA) alongside measurements of bacterial (leucine incorporation) and fungal (acetate in ergosterol incorporation) growth rates, previously shown to be highly responsive to changes in environmental factors, and microbial respiration. We found no legacy effects on the microbial community size, composition, growth rates, or basal respiration rates at the effect sizes used in our experimental setup (0.6 °C, about 30% precipitation reduction). Our findings support previous reports from single short‐term ecosystem studies thereby providing a clear evidence base to allow long‐term, broad‐scale generalizations to be made. The implication of our study is that warming and summer drought will not result in legacy effects on the microbial community and their processes within the effect sizes here studied. While legacy effects on microbial processes during perturbation cycles, such as drying–rewetting, and on tolerance to drought and warming remain to be studied, our results suggest that any effects on overall ecosystem processes will be rather limited. Thus, the legacies of warming and drought should not be prioritized factors to consider when modeling contemporary rates of biogeochemical processes in soil. 相似文献