Jean‐Marc LimousinAmélie RousselJesús Rodríguez‐CalcerradaJosé M. Torres‐Ruiz...
18页
查看更多>>摘要：Abstract Increasing temperature and drought can result in leaf dehydration and defoliation even in drought‐adapted tree species such as the Mediterranean evergreen Quercus ilex L. The stomatal regulation of leaf water potential plays a central role in avoiding this phenomenon and is constrained by a suite of leaf traits including hydraulic conductance and vulnerability, hydraulic capacitance, minimum conductance to water vapour, osmotic potential and cell wall elasticity. We investigated whether the plasticity in these traits may improve leaf tolerance to drought in two long‐term rainfall exclusion experiments in Mediterranean forests. Osmotic adjustment was observed to lower the water potential at turgor loss in the rainfall‐exclusion treatments, thus suggesting a stomatal closure at more negative water potentials and a more anisohydric behaviour in drier conditions. Conversely, leaf hydraulic conductance and vulnerability did not exhibit any plasticity between treatments so the hydraulic safety margins were narrower in the rainfall‐exclusion treatments. The sequence of leaf responses to seasonal drought and dehydration was conserved among treatments and sites but trees were more likely to suffer losses of turgor and hydraulic functioning in the rainfall‐exclusion treatments. We conclude that leaf plasticity might help the trees to tolerate moderate drought but not to resist severe water stress.
查看更多>>摘要：Abstract Adaptation of higher plants to extreme environmental conditions is under complex regulation. Several small peptides have recently been described to modulate responses to stress conditions. The Small Paraquat resistance protein (SPQ) of Lepidium crassifolium has previously been identified due to its capacity to confer paraquat resistance to overexpressing transgenic Arabidopsis plants. Here, we show?that overexpression of the closely related Arabidopsis SPQ can also enhance resistance to paraquat, while the Arabidopsis spq1 mutant is slightly hypersensitive to this herbicide. Besides being implicated in paraquat response, overexpression of SPQs enhanced sensitivity to abscisic acid (ABA), and the knockout spq1 mutant was less sensitive to ABA. Both Lepidium‐ and Arabidopsis‐derived SPQs could improve drought tolerance by reducing water loss, stabilizing photosynthetic electron transport?and enhancing plant viability and survival in a water‐limited environment. Enhanced drought tolerance of SPQ‐overexpressing plants could be confirmed by characterizing various parameters of growth, morphology and photosynthesis using an automatic plant phenotyping platform with RGB and chlorophyll fluorescence imaging. Our results suggest that SPQs can be regulatory small proteins connecting ROS and ABA regulation and through that influence responses to certain stresses.
查看更多>>摘要：Abstract The FYVE domain protein required for endosomal sorting 1 (FREE1), which was previously identified as a plant‐specific component of the endosomal sorting complex required for transport machinery, plays an essential role in endosomal trafficking. Moreover, FREE1 also functions as an important negative regulator in abscisic acid (ABA) signalling. Multiple phosphorylations and ubiquitination sites have been identified in FREE1, hence unveiling the factors involved in posttranslational regulation of FREE1 is critical for comprehensively understanding FREE1‐related regulatory networks during plant growth. Here, we demonstrate that plant‐specific casein kinase I?members MUT9‐like kinases 1–4 (MLKs 1–4)/Arabidopsis EL1‐like 1–4 interact with and phosphorylate FREE1 at serine residue S582, thereby modulating the nuclear accumulation of FREE1. Consequently, mutation of S582 to non‐phosphorylable residue results in reduced nuclear localization of FREE1 and enhanced ABA response. In addition, mlk123 and mlk134 triple mutants accumulate less FREE1 in the nucleus and display hypersensitive responses to ABA treatment, whereas overexpression of the nuclear‐localized FREE1 can restore the ABA sensitivity of seedling establishment in mlks triple mutants. Collectively, our study demonstrates a previously unidentified function of MLKs in attenuating ABA signalling in the nucleus by regulating the phosphorylation and nuclear accumulation of FREE1.
查看更多>>摘要：Abstract Canola varieties exhibit variation in drought avoidance and drought escape traits, reflecting adaptation to water‐deficit environments. Our understanding of underlying genes and their interaction across environments in improving crop productivity is limited. A doubled haploid?population was analysed to identify quantitative trait loci?(QTL) associated with water‐use efficiency (WUE) related traits. High WUE in the vegetative phase was associated with low seed yield. Based on the resequenced parental genome data, we developed sequence‐capture‐based markers and validated their linkage with carbon isotope discrimination (Δ13C) in an F2 population. RNA?sequencing was performed to determine the expression of candidate genes underlying Δ13C QTL. QTL contributing to main and QTL?×?environment interaction effects for Δ13C and yield were identified. One multiple‐trait QTL for Δ13C, days to flower, plant height, and seed yield was identified on chromosome A09. Interestingly, this QTL region overlapped with a homoeologous exchange?(HE) event, suggesting its association with the multiple traits. Transcriptome analysis revealed 121 significantly differentially expressed genes underlying Δ13C QTL on A09 and C09, including in HE regions. Sorting out the negative relationship?between vegetative WUE and seed yield is a priority. Genetic and genomic resources and knowledge so developed could improve canola WUE and yield.
Celia M. Rodriguez‐DominguezAlicia FornerSebastia MartorellBrendan Choat...
25页
查看更多>>摘要：Abstract Leaf water potential (ψleaf), typically measured using the pressure chamber, is the most important metric of plant water status, providing high theoretical value and information content for multiple applications in quantifying critical physiological processes including drought responses. Pressure chamber measurements of ψleaf (ψleafPC) are most typical, yet, the practical complexity of the technique and of the underlying theory has led to ambiguous understanding of the conditions to optimize measurements. Consequently, specific techniques and precautions diversified across the global research community, raising questions of reliability and repeatability. Here, we surveyed specific methods of ψleafPC from multiple laboratories, and synthesized experiments testing common assumptions and practices in ψleafPC for diverse species: (i) the need for equilibration of previously transpiring leaves; (ii) leaf storage before measurement; (iii) the equilibration of ψleaf for leaves on bagged branches of a range of dehydration; (iv) the equilibration of ψleaf across the lamina for bagged leaves, and the accuracy of measuring leaves with artificially ‘elongated petioles’; (v) the need in ψleaf measurements for bagging leaves and high humidity within the chamber; (vi) the need to avoid liquid water on leaf surfaces; (vii) the use of ‘pulse’ pressurization versus gradual pressurization; and (viii) variation among experimenters in ψleafPC determination. Based on our findings we provide a best practice protocol to maximise accuracy, and provide recommendations for ongoing species‐specific tests of important assumptions in future studies.
Liang FangXinyou YinPeter E. L. PuttenPierre Martre...
16页
查看更多>>摘要：Abstract We assessed how the temperature response of leaf day respiration (Rd) in wheat responded to contrasting water regimes and growth temperatures. In Experiment 1, well‐watered and drought‐stressed conditions were imposed on two genotypes; in Experiment 2, the two water regimes combined with high (HT), medium (MT) and low (LT) growth temperatures were imposed on one of the genotypes. Rd was estimated from simultaneous gas exchange and chlorophyll fluorescence measurements at six leaf temperatures (Tleaf) for each treatment, using the Yin method for nonphotorespiratory conditions and the nonrectangular hyperbolic fitting method for photorespiratory conditions. The two genotypes responded similarly to growth and measurement conditions. Estimates of Rd for nonphotorespiratory conditions were generally higher than those for photorespiratory conditions, but their responses to Tleaf were similar. Under well‐watered conditions, Rd and its sensitivity to Tleaf slightly acclimated to LT, but did not acclimate to HT. Temperature sensitivities of Rd were considerably suppressed by drought, and the suppression varied among growth temperatures. Thus, it is necessary to quantify interactions between drought and growth temperature for reliably modelling Rd under climate change. Our study also demonstrated that the Kok method, one of the currently popular methods for estimating Rd, underestimated Rd significantly.
Kevin L. GriffinZoe M. GriffinStephanie C. SchmiegeSarah G. Bruner...
15页
查看更多>>摘要：Abstract White spruce (Picea glauca) spans a massive range, yet the variability in respiratory physiology and related implications for tree carbon balance at the extremes of this distribution remain as enigmas. Working at both the most northern and southern extents of the distribution range more than 5000?km apart, we measured the short‐term temperature response of dark respiration (R/T) at upper and lower canopy positions. R/T curves were fit to both polynomial and thermodynamic models so that model parameters could be compared among locations, canopy positions, and with previously published data. Respiration measured at 25°C (R25) was 68% lower at the southern location than at the northern location, resulting in a significantly lower intercept in R/T response in temperate trees. Only at the southern location did upper canopy leaves have a steeper temperature response than lower canopy leaves, likely reflecting canopy gradients in light. At the northern range limit respiration is nearly twice that of the average R25 reported in a global leaf respiration database. We predict that without significant thermal acclimation, respiration will increase with projected end‐of‐the‐century warming and will likely constrain the future range limits of this important boreal species.
查看更多>>摘要：Abstract Light stress is one of the important stresses for winter survival in evergreens, especially for plants with broad leaves, like evergreen rhododendrons. Photoprotection has been shown to upregulate dramatically in rhododendrons during winter, but whether it directly contributes to enhancing the freezing tolerance is still unknown. In this study, we found that the expression and circadian rhythm of an early light‐induced protein (ELIP)—RhELIP3—which exerts photoprotection in Rhododendron ‘Elsie Lee’, could be impacted by both photoperiod and low temperature, with low temperature being the predominant inducer. Arabidopsis overexpressing RhELIP3 displayed significantly stronger freezing tolerance and better photosystem II function after a 3‐day recovery from freezing treatment. Moreover, RhHY5 binds with the?RhELIP3 promoter to activate its expression. Arabidopsis overexpressing RhHY5 exhibited stronger freezing tolerance and better photosystem II function. AtELIP1 and AtELIP2 were significantly induced in RhHY5‐overexpressed Arabidopsis at low temperatures. We also discovered that RhBBX24 binds directly to RhELIP3 promoter and suppresses its expression. RhBBX24 can also interact with RhHY5 and inhibit the interaction of RhHY5–RhELIP3. RhELIP3, RhHY5,?and RhBBX24 exhibited similar circadian rhythms under low temperature with short period. Overall, our investigation highlights that photoprotection is involved in improving the freezing tolerance of evergreen rhododendrons.
查看更多>>摘要：Abstract To explore diversity in cold hardiness mechanisms, high resolution magnetic resonance imaging (MRI) was used to visualise freezing behaviours in wintering Daphne kamtschatica var. jezoensis flower buds, which have naked florets and no bud scales. MRI images showed that anthers remained stably supercooled to the range from ?14 to ?21°C or lower while most other tissues froze by ?7°C. Freezing of some anthers detected in MRI images between ?14 and ?21°C corresponded with numerous low temperature exotherms and also with the ‘all‐or‐nothing’ type of anther injuries. In ovules/pistils, only embryo sacs remained supercooled at ?7°C or lower, but slowly dehydrated during further cooling. Cryomicroscopic observation revealed ice formation in the cavities of calyx tubes and pistils but detected no ice in embryo sacs or in anthers. The distribution of ice nucleation activity in floral tissues corroborated the tissue freezing behaviours. Filaments likely work as the ice blocking barrier that prevents ice intrusion from extracellularly frozen calyx tubes to connecting unfrozen anthers. Unique freezing behaviours were demonstrated in Daphne flower buds: preferential freezing avoidance in male and female gametophytes and their surrounding tissues (by stable supercooling in anthers and by supercooling with slow dehydration in embryo sacs) while the remaining tissues tolerate extracellular freezing.
NSTL
Wiley