Snider, John L.Pilon, CristianeHu, WeiWang, Hai-Miao...
12页
查看更多>>摘要：Temperatures between 10 degrees C and 25 degrees C limit seedling growth and reversibly inhibit net assimilation (A(N)) in cold sensitive plants. Because A(N) represents multiple component processes operating in a highly concerted manner, quantifying the cold sensitivities of each constituent would provide targets for improving cold tolerance. To address this, Gossypium hirsutum (cotton) seedlings grown under sub-optimal temperatures (20/15 degrees C) exhibited substantial declines in plant growth, A(N), and nearly every thylakoid process assessed, relative to optimal conditions (30/20 degrees C). In contrast, energy dissipation by photosystem II (PSII) increased under low temperature concomitant with a rise in carotenoid content, hydrogen peroxide production, and ascorbate peroxidase activity. Temperature response experiments defined the temperature needed for 50% reductions in activity for a given process (T-50). Respiration (R-D) was the most cold-sensitive process followed by thylakoid-dependent processes and gross photosynthesis (A(G)), whereas A(N) was the most-cold tolerant process evaluated. A(N)-C-i experiments revealed that carboxylation was more cold-sensitive than RuBP regeneration. Maximum quantum yield of photosystem II was insensitive to low incubation temperature (F-v/F-m), and T-50 could not be estimated. Low temperature-grown plants also exhibited a 1.5 degrees C increase in T-50 for R-D, a 2.5 degrees C decrease in T-50 for thylakoid-dependent processes and A(G), and a 3.4 degrees C decrease in T-50 for A(N). Thus, the current study defines the relative cold sensitivities of the underlying processes driving A(N). Additionally, it is concluded that A(N) acclimates to low growth temperature more than any other process evaluated due to increased cold sensitivity of R-D and increased cold tolerance of thylakoid dependent processes and A(G).
查看更多>>摘要：NAC transcription factors play critical roles in regulating drought stress. However, the drought-responsive NAC transcription factors are largely unexplored in wheat. In this study, we isolated a NAC gene, TaNAC5D-2, and characterized the function of TaNAC5D-2 as a positive regulator of drought tolerance. The expression level of TaNAC5D-2 was induced under drought or abscisic acid treatment. Transient expression and transcriptional activity assays showed that TaNAC5D-2 is localized to the nucleus, and the C-terminal region exhibited transcriptional activity. Overexpression of TaNAC5D-2 in Arabidopsis thaliana led to greater drought tolerance, fresh weight and dry weight than wild-type plants, and the water loss was significant inhibited in the leaves of overexpression lines. Conversely, silencing of TaNAC5D-2 in wheat seedlings led to increased water loss and decreased growth compared to control and negative control plants under drought stress. RNA-Seq and RT-qPCR revealed that many Group A PP2C genes were upregulated in the TaNAC5D-2 silenced plants compared to negative control. And silencing TaNAC5D-2 negatively regulate ABA-induced stomatal closure that led to higher water loss. These data suggest that TaNAC5D-2 acts as a drought-responsive regulator, possibly by an abscisic acid-mediated stomatal closure to control water loss under drought condition.
查看更多>>摘要：Secondary metabolites, such as flavonoids, are key participants in biotic and abiotic stress responses in plants. Production of Flavonol Glycosides 3 (PFG3), an R2R3-MYB transcription factor, has been reported to regulate flavonoid biosynthesis and accumulation in Arabidopsis, but its role in drought and other stress responses remains unclear. In this study, we created PFG3-deficient mutants (pfg3 and pfg3-d1) to investigate how PFG3 influences plant flavonoid synthesis and drought/osmotic stress responses. PFG3 was localized in the nucleus and had transcriptional activator activity. The transcript levels of key flavonoid synthesis genes were significantly reduced in pfg3 and pfg3-d1. PFG3 was expressed mainly in leaves, and its expression was induced by osmotic stress. pfg3 and pfg3-d1 showed impaired accumulation of flavonoids, especially flavonols, and were more sensitive to osmotic and drought stresses. The pfg3 and pfg3-d1 mutants showed less biomass accumulation and a weaker ability to acclimate during drought treatment compared with Col-0 plants. Taken together, our data show that PFG3 is important for plant drought/osmotic stress tolerance by regulating flavonoid biosynthesis.
查看更多>>摘要：Perennial ryegrass (Lolium perenne L.) is widely used as cool-season turfgrass; however, its growth is mainly limited by cold and drought stress. The interplay between melatonin and brassinosteroids in enhancing tolerance to cold and drought stress and their underlying molecular mechanisms is poorly understood so far. In this study, melatonin enhanced cold and drought tolerance in perennial ryegrass depended on the duration of dose and the level of stress. Although melatonin activates the expression of NADPH oxidase-related genes post-exposure to short-term cold/drought stresses, the accumulation of H2O2 was reduced under long-term stress. This increase in antioxidant activity was correlated with an increase of genes expressed in their antioxidant system and ascorbate-glutathione cycle. Moreover, the exogenous melatonin induced the biosynthesis of melatonin and brassinoste-roids or the expression of signaling-related genes. However, the expression of brassinosteroids biosynthesis and signaling-related genes were inhibited in the rbohC and rbohF mutants in the presence of melatonin. The inhi-bition of H2O2 production attenuated melatonin-mediated growth in the Arabidopsis wild-type as well as bak1 and bri1.9 mutants. DMTU inhibited the mitigation effect of melatonin on the H2O2 accumulation in WT and LpBAK1 transgenic plants, while a lighter DAB staining was observed in the LpBAK1 transgenic seedlings. Consistently, the chemical scavenging of H2O2 impaired the effect of melatonin as well as brassinosteroids on seed germination and the root growth of perennial ryegrass. The current study reveals a novel regulatory mechanism of the crosstalk between H2O2 and brassinosteroid signaling in melatonin-induced cold/drought tolerance in perennial ryegrass.
NSTL
Elsevier