An integrative proteome analysis of different seedling organs in tolerant and sensitive wheat cultivars under drought stress and recovery

Roots, leaves, and intermediate sections between roots and leaves (ISRL) of wheat seedlings show different physiological functions at the protein level. We performed the first integrative proteomic analysis of different tissues of the drought‐tolerant wheat cultivar Hanxuan 10 (HX‐10) and drought‐sensitive cultivar Chinese Spring (CS) during a simulated drought and recovery. Differentially expressed proteins (DEPs) in the roots (122), ISRLs (146), and leaves (163) showed significant changes in expression in response to drought stress and recovery. Numerous DEPs associated with cell defense and detoxifications were significantly regulated in roots and ISRLs, while in leaves, DEPs related to photosynthesis showed significant changes in expression. A significantly larger number of DEPs related to stress defense were upregulated in HX‐10 than in CS. Expression of six HSPs potentially related to drought tolerance was significantly upregulated under drought conditions, and these proteins were involved in a complex protein–protein interaction network. Further phosphorylation analysis showed that the phosphorylation levels of HSP60, HSP90, and HOP were upregulated in HX‐10 under drought stress. We present an overview of metabolic pathways in wheat seedlings based on abscisic acid signaling and important protein expression patterns.     

土壤干旱条件下不同施钾水平对烟草光合速率和蒸腾效率的影响

研究了土壤干旱条件下,不同的施钾水平对烟草光合速率,胞间CO2浓度,气孔导度,蒸腾速率,蒸腾效率及生物量的影响。结果表明：在土壤干旱条件下适量施钾可以减少叶肉细胞光合活性的下降,消弱非气孔因素对光合的限制,增强气孔调节能力,提高蒸腾效率,并获得较高的生物量。     

Salinity and drought tolerance of mannitol-accumulating transgenic tobacco

Tobacco plants (Nicotiana tabacum L.) were transformed with a mannitol-1-phosphate dehydrogenase gene resulting in mannitol accumulation. Experiments were conducted to determine whether mannitol provides salt and/or drought stress protection through osmotic adjustment. Non-stressed transgenic plants were 20–25% smaller than non-stressed, non-transformed (wild-type) plants in both salinity and drought experiments. However, salt stress reduced dry weight in wild-type plants by 44%, but did not reduce the dry weight of transgenic plants. Transgenic plants adjusted osmotically by 0.57 MPa, whereas wild-type plants did not adjust osmotically in response to salt stress. Calculations of solute contribution to osmotic adjustment showed that mannitol contributed only 0-003-0-004 MPa to the 0.2 MPa difference in full turgor osmotic potential (π_o) between salt-stressed transgenic and wild-type plants. Assuming a cytoplasmic location for mannitol and that the cytoplasm constituted 5% of the total water volume, mannitol accounted for only 30–40% of the change in π_o of the cytoplasm. Inositol, a naturally occurring polyol in tobacco, accumulated in response to salt stress in both transgenic and wild-type plants, and was 3-fold more abundant than mannitol in transgenic plants. Drought stress reduced the leaf relative water content, leaf expansion, and dry weight of transgenic and wild-type plants. However, π_o was not significantly reduced by drought stress in transgenic or wild-type plants, despite an increase in non-structural carbohydrates and mannitol in droughted plants. We conclude that (1) mannitol was a relatively minor osmolyte in transgenic tobacco, but may have indirectly enhanced osmotic adjustment and salt tolerance; (2) inositol cannot substitute for mannitol in this role; (3) slower growth of the transgenic plants, and not the presence of mannitol per se, may have been the cause of greater salt tolerance, and (4) mannitol accumulation was enhanced by drought stress but did not affect π_o or drought tolerance.     

干旱胁迫对3种灌木不同器官化学计量特征的影响

采用盆栽控水试验,研究了3个水分处理,即田间持水量(FC)的(75±5)％、(55±5)％和(35±5)％,对丁香、黄刺梅、连翘的叶、茎、极细根(0～1 mm)、细根(1～2 mm)和粗根(＞2 mm)化学计量特征的影响.结果表明:3种灌木相同器官间氮(N)和磷(P)含量以及C∶N、C∶P、N∶P均存在显著差异.随着干...     

Seed priming of plants aiding in drought stress tolerance and faster recovery: a review

Plant Growth Regulation - Drought stress exposure adversely affects plant growth and productivity. Various seed priming techniques are experimented to mitigate the adverse effect of drought stress...     

不同西瓜基因型对干旱胁迫的生理响应及其抗旱性评价

以来源于不同地区的12个西瓜基因型为试材,采用盆栽控水的方式进行持续干旱处理,研究干旱胁迫对西瓜幼苗株高、根长、鲜质量及干物质积累等生长状况的影响,比较不同基因型材料对干旱胁迫的生理响应差异,同时依据旱害指数对其抗旱性进行直接评价,并采用隶属函数法进一步验证和综合评价.结果表明: 干旱处理下,12个西瓜基因型对干旱胁迫的耐受能力存在明显差异,各基因型开始出现旱害症状的时间和发生旱害的程度各不相同.干旱胁迫降低了西瓜幼苗的株高、地上、地下鲜质量和地上干物质积累量,普遍提高了根冠比,而对根长和地下干质量存在正向和负向两种不同的影响.干旱处理后,西瓜叶片的相对含水量和叶绿素含量均不同程度降低,丙二醛、过氧化氢和超氧阴离子含量增加,脯氨酸大量积累,而可溶性蛋白含量以及抗氧化酶活性则因基因型的不同而表现出不同的结果.分析认为,3个野生型材料M20、KY-3和Y-2为抗旱性强的西瓜种质,Y34、金美人和04-1-2为敏感种质,而其余基因型为中抗种质.     

An Arabidopsis mitochondrial uncoupling protein confers tolerance to drought and salt stress in transgenic tobacco plants

Background

Plants are challenged by a large number of environmental stresses that reduce productivity and even cause death. Both chloroplasts and mitochondria produce reactive oxygen species under normal conditions; however, stress causes an imbalance in these species that leads to deviations from normal cellular conditions and a variety of toxic effects. Mitochondria have uncoupling proteins (UCPs) that uncouple electron transport from ATP synthesis. There is evidence that UCPs play a role in alleviating stress caused by reactive oxygen species overproduction. However, direct evidence that UCPs protect plants from abiotic stress is lacking.

Methodology/Principal Findings

Tolerances to salt and water deficit were analyzed in transgenic tobacco plants that overexpress a UCP (AtUCP1) from Arabidopsis thaliana. Seeds of AtUCP1 transgenic lines germinated faster, and adult plants showed better responses to drought and salt stress than wild-type (WT) plants. These phenotypes correlated with increased water retention and higher gas exchange parameters in transgenic plants that overexpress AtUCP1. WT plants exhibited increased respiration under stress, while transgenic plants were only slightly affected. Furthermore, the transgenic plants showed reduced accumulation of hydrogen peroxide in stressed leaves compared with WT plants.

Conclusions/Significance

Higher levels of AtUCP1 improved tolerance to multiple abiotic stresses, and this protection was correlated with lower oxidative stress. Our data support previous assumptions that UCPs reduce the imbalance of reactive oxygen species. Our data also suggest that UCPs may play a role in stomatal closure, which agrees with other evidence of a direct relationship between these proteins and photosynthesis. Manipulation of the UCP protein expression in mitochondria is a new avenue for crop improvement and may lead to crops with greater tolerance for challenging environmental conditions.     

Myosmine in different organs of tobacco plant

Myosmine was found to be present in different organs of tobacco plant by TLC. Myosmine is a natural minor alkaloid of tobacco plant; it is not a decomposition product nor a 'smoke' alkaloid.     

干旱胁迫对不同耐旱性玉米杂交种产量和根系生理特性的影响

通过盆栽人工模拟干旱试验,研究了全生育期中度干旱胁迫对不同耐旱性玉米杂交种（耐旱：京科628;不耐旱：农大95）产量及根系生理特性的影响.结果表明：干旱胁迫下,耐旱玉米产量比对照减少33.7%,不耐旱玉米则比对照减少62.3%.干旱胁迫下,玉米根系生物量降低且最大值出现时间提前,与对照相比,不耐旱玉米根冠比升高,耐旱玉米根冠比前期升高后期降低;根系活力降低,不耐旱玉米根系活力降低幅度大于耐旱玉米;根系超氧化物歧化酶（SOD）活性前期高于对照后期低于对照,耐旱玉米根系SOD活性开始低于对照的时间比不耐旱玉米晚;根系丙二醛（MDA）含量升高,随干旱胁迫处理时间的延长,不耐旱玉米MDA含量比对照升高的幅度大于耐旱玉米;根系可溶性蛋白含量降低,不耐旱玉米的降低幅度大于耐旱玉米.干旱胁迫下耐旱玉米杂交种根系活力﹑根系SOD活性及可溶性蛋白含量较高,减缓了根系的衰老进程,延长了根系功能期,这可能是耐旱玉米杂交种在干旱胁迫下仍能获得较高产量的重要原因之一.     

Recent methods of drought stress tolerance in plants

In the climate change scenario the drought has been diagnosed as major stress affecting crop productivity. This review demonstrates some recent findings on the amelioration of drought stress. Nanoparticles, synthetic growth regulators viz. Trinexapac-ethyl, and Biochar addition helps to economize the water budget of plants, enhances the bioavailability of water and nutrients as well as overcomes drought induced osmotic and oxidative stresses. Besides ABA, SA and JA are also involved in inducing tolerance to drought stress through modulation of physiological and biochemical processes in plants. Plant growth promoting rhizobacteria (PGPR) offer new opportunities in agricultural biotechnology. These beneficial microorganisms colonize the rhizosphere/endo-rhizosphere of plants and impart drought tolerance by improving root architechture, enhancing water use efficiency, producing exopolysaccharides, phytohormones viz, ABA, SA and IAA and volatile compounds. Further PGPR also play positive role in combating osmotic and oxidative stresses induced by drought stress through enhancing the accumulation of osmolytes, antioxidants and upregulation or down regulation of stress responsive genes. In transgenic plants stress inducible genes enhanced abiotic stress tolerance by encoding key enzymes regulating biosynthesis of compatible solutes. The role of genes/cDNAs encoding proteins involved in regulating other genes/proteins, signal transduction process and strategies to improve drought stress tolerance have also been discussed.     

Effects of mycorrhizal infection on drought tolerance and recovery in safflower and wheat

The influence of arbuscular mycorrhizal fungi on drought tolerance and recovery was studied in safflower (Carthamus tinctorius L.) and wheat (Triticum aestivum L.). Plants were grown with and without the mycorrhizal fungus, Glomus etunicatum Becker & Gerd., in nutrient-amended soil under environmentally-controlled conditions to yield mycorrhizal and nonmycorrhizal with similar leaf areas, root length densities, dry weights, and adequate tissue phosphorus. When drought stress was induced, mycorrhizal infection did not affect changes in leaf water, osmotic or pressure potentials, or osmotic potentials of leaf tissue rehydrated to full turgor in either safflower or wheat. Furthermore, in safflower, infection had little effect on drought tolerance as indicated by the level of leaf necrosis. Mycorrhizal wheat plants, however, had less necrotic leaf tissue than uninfected plants at moderate levels of drought stress (but not at severe levels) probably due to enhanced phosphorus nutrition. To determine the effects of infection on drought recovery, plants were rewatered at a range of soil water potentials from –1 to –4 MPa. We found that although safflower tended to recover more slowly from drought after rewatering than wheat, mycorrhizal infection did not directly affect drought recovery in either plant species. Daily water use after rewatering was reduced and was correlated to the extent that leaves were damaged by drought stress in both plant species, but was not directly influenced by the mycorrhizal status of the plants.     

GbMPK3, a mitogen-activated protein kinase from cotton,enhances drought and oxidative stress tolerance in tobacco

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules found in all eukaryotes, and play significant roles in developmental and environmental signal transduction. In this study, a MAPK gene (GbMPK3), which showed homologous to AtMPK3 and NtWIPK, was isolated from sea-island cotton (Gossypium barbadense) and induced during multiple abiotic stress treatments including salt, cold, heat, dehydration and oxidative stress. Transgenic tobacco (Nicotiana benthamiana) with constitutively higher expression of GbMPK3 was conferred with enhanced drought tolerance, reduced water loss during drought treatment and improved plant height and survival rates after re-watering. Additionally, the gene expression levels and enzymatic activity of antioxidant enzymes were more strongly induced with depressed hydrogen peroxide accumulation in GbMPK3-overexpressing tobacco compared with wild-type under drought condition. Furthermore, observation of seed germination and leaf morphology showed that tolerance of transgenic plants to methyl viologen was improved due to increased antioxidant enzyme expression, suggesting that GbMPK3 may positively regulate drought tolerance through enhanced reactive oxygen species scavenging ability.     

Photosynthetic gas exchange characteristics in three different almond species during drought stress and subsequent recovery

Three different drought stress levels (water potential of the nutrient solution, Ψ_s = −0.6, −1.2 and −1.8 MPa, respectively), and a control treatment (Ψ_s = −0.1 MPa), were applied during 2 weeks to three almond species, followed by 3 weeks of recovery. The selected test species were Prunus dulcis (Miller) D.Webb (bitter almond) and two wild almond species, P. lycioides (Spach) C.K. Schneider and P. scoparia (Spach) C.K. Schneider. All three are species native to Iran, and can be used as rootstock, but only P. dulcis is actually used for commercial almond production.In the absence of drought stress, maximum net assimilation rate (A_max) is highest for P. scoparia and lowest for P. dulcis. For all species A_max was above 16 μmol CO₂ m⁻² s⁻¹. A similar relationship between A_max and dark respiration rate (R_d), was observed for all species. This relationship suggests that optimisation of the carbon budget is independent of species.The three investigated species seem to have a different reaction to a similar stress, indicating different drought stress coping strategies. P. scoparia lost all its leaves during the experiment, while P. lycioides only kept some leaves, however, the remaining leaves were almost totally wilted and did not allow for any photosynthesis measurement. P. scoparia did not recover during the experiment, as no new leaves were developed once Ψ_s was restored to pre-drought stress levels. However, this species has green stems, indicating that stem photosynthesis might play an important role in the plants’ overall carbon balance. This species is an opportunistic one (sensu [Higgins, S.S., Larsen, F.E., Bendel, R.B., Radamaker, G.K., Bassman, J.H., Bidlake, W.R., Alwir, A., 1992. Comparative gas-exchange characteristics of potted, glasshouse-grown almond, apple, fig, grape, olive, peach and Asian pear. Sci. Hortic. 52 (4), 313–329]), where assimilation is seriously limited by non-stomatal processes as evidenced by measurements of intercellular CO₂ concentration, eventually resulting in total leaf loss. All P. lycioides leaves almost completely wilted during the experiment, but this species recovered rather quickly. Leaves, newly formed at the end of the experiment, obtained maximal assimilation rates under control Ψ_s levels, equivalent to those measured in the control treatment. Finally, P. dulcis did keep at least part of its leaves during drought stress. However, assimilation rates after 2 weeks of drought treatment and 3 weeks of recovery were only about half of those measured in the control treatment. Of the three investigated species, non-stomatal limitation of assimilation seems to be the least important in P. dulcis.Intrinsic water use efficiency, defined as the ratio of assimilation rate over stomatal conductance, increased for P. dulcis with increasing drought stress, while a different pattern was observed for P. lycioides and P. scoparia, indicating non-stomatal processes prevail over stomatal limitations of the assimilation process. It was concluded that P. dulcis is the species most tolerant to drought. P. scoparia tries to avoid drought, whereas P. lycioides has an intermediate behaviour. Besides P. dulcis, also P. lycioides seems to have some potential for use as rootstock for commercial almond production.