【目的】探索高原环境下青稞花后干旱胁迫响应模型及青稞受旱程度的快速、有效的检测方法，为青稞节水高产栽培提供理论依据和技术参考。【方法】利用干旱棚进行青稞盆栽模拟花后干旱，设轻度（对照灌水量的75%，LD）、中度（对照灌水量的50%，MD）和重度（对照灌水量的25%，HD）干旱胁迫处理，采用WP4C水势仪、LI-6400XT和OS5P便携式脉冲调制叶绿素荧光仪，分别测定叶水势（LWP）、叶蒸发冷却值（ΔT）、光合气体交换参数和叶绿素荧光变量；成熟后获取产量数据；利用数字图像法对籽粒表型进行定量分析，并依粒二维面积大小将籽粒划分大、中、小3个粒级。【结果】干旱水平与叶水势呈线性正相关，而与叶蒸发冷却值（ΔT）呈线性显著负相关（P＜0.05），两者均能灵敏反映青稞受旱程度。LD、MD和HD处理与CK相比，干旱胁迫导致旗叶净光合速率（P_n）、气孔导度（g_s）、胞间CO₂浓度（C_i）、蒸腾速率（T_r）、最大荧光（F_m）、PS II的最大量子效率（F_v/F_m）、PS II的实际光量子产量（ΦPSII）、光化学淬灭（qP）、光合电子传递的相对速率（ETR）呈降低趋势，而气孔限制（L_s）、初始荧光（F_o）、非光化学淬灭（NPQ）呈上升趋势，且MD和HD处理较CK对以上参数差异明显。随着干旱胁迫的加重，青稞千粒重、籽粒产量、单株粒重、干物质积累量和经济系数降低趋势愈明显。相关分析表明，干旱胁迫诱导g_s降低，直接导致?T上升，间接引起FWP下降，使得F_o、NPQ上升，F_m、F_v/F_m、ΦPSII、ETR、qP和P_n降低，进而引起粒二维面积、粒周长、粒长和粒宽减小，而粒圆度值增大；小粒占比明显增加，而大粒占比明显下降。【结论】LWP和?T对青稞花后干旱胁迫反映灵敏，可作为评价其受旱的指标。随着干旱胁迫加重，青稞旗叶光合和叶绿素荧光参数的变化加大，并造成5个籽粒表型性状值及粒级逐渐减小，最终导致千粒重、单穗粒重、籽粒产量、干物质积累量和经济系数下降。

干旱胁迫是抑制植物生长发育的主要限制因子之一，植物为适应干旱的外界环境，会依据自身的习性启动响应机制。从植物外部形态、生理代谢、生化过程、细胞及分子水平的变化阐述了植物对干旱胁迫的响应机制，详细阐述了生理及分子水平的响应机制，并对分子和遗传水平的响应机制和植物抗旱性关系的未来研究方向提出了展望，以期为植物抗逆性及遗传育种研究提供参考。

Climate change is altering the availability of resources and the conditions that are crucial to plant performance. One way plants will respond to these changes is through environmentally induced shifts in phenotype (phenotypic plasticity). Understanding plastic responses is crucial for predicting and managing the effects of climate change on native species as well as crop plants. Here, we provide a toolbox with definitions of key theoretical elements and a synthesis of the current understanding of the molecular and genetic mechanisms underlying plasticity relevant to climate change. By bringing ecological, evolutionary, physiological and molecular perspectives together, we hope to provide clear directives for future research and stimulate cross-disciplinary dialogue on the relevance of phenotypic plasticity under climate change.Copyright © 2010 Elsevier Ltd. All rights reserved.

Abscisic acid (ABA) metabolism, perception, and transport form a triptych allowing higher plants to use ABA as a signaling molecule. The molecular bases of ABA metabolism are now well described and, over the past few years, several ABA receptors have been discovered. Although ABA transport has long been demonstrated in planta, the first breakthroughs in identifying plasma membrane-localized ABA transporters came in 2010, with the identification of two ATP-binding cassette (ABC) proteins. More recently, two ABA transporters in the nitrate transporter 1/peptide transporter (NRT1/PTR) family have been identified. In this review, we discuss the role of these different ABA transporters and examine the scientific impact of their identification. Given that the NRT1/PTR family is involved in the transport of nitrogen (N) compounds, further work should determine whether an interaction between ABA and N signaling or nutrition occurs.Copyright © 2013 Elsevier Ltd. All rights reserved.

Abscisic acid (ABA) is a potent molecule that certainly modifies stomatal behaviour and plant water loss and probably acts to modify the growth of leaves. The hormone is synthesized both in the leaves and the roots of the plant and in the soil and may move freely from plant to soil and soil to plant. It can also move rapidly through the plant in both the xylem and the phloem and will partition between different compartments in different tissues largely as a function of pH. It is described here how perturbations in soil conditions around the roots and the water status of the air can modify the fluxes of ABA around the plant and its accumulation in different compartments and different tissues. These fluxes can be interpreted as signals of different stresses imposed on the plant and consideration is given to how different perturbations can exert subtle changes which are manifest as modified shoot growth rates and functioning. Most emphasis in the discussion is placed upon the plant's responses to the imposition of soil and atmospheric drought.

There is now strong evidence that the plant hormone abscisic acid (ABA) plays an important role in the regulation of stomatal behaviour and gas exchange of droughted plants. This regulation involves both long‐distance transport and modulation of ABA concentration at the guard cells, as well as differential responses of the guard cells to a given dose of the hormone. We will describe how a plant can use the ABA signalling mechanism and other chemical signals to adjust the amount of water that it loses through its stomata in response to changes in both the rhizospheric and the aerial environment. The following components of the signalling process can play an important part in regulation: (a) ABA sequestration in the root; (b) ABA synthesis versus catabolism in the root; (c) the efficiency of ABA transfer across the root and into the xylem; (d) the exchange of ABA between the xylem lumen and the xylem parenchyma in the shoot; (e) the amount of ABA in the leaf symplastic reservoir and the efficiency of ABA sequestration and release from this compartment as regulated by factors such as root and leaf‐sourced changes in pH; (f) cleavage of ABA from ABA conjugates in the leaf apoplast; (g) transfer of ABA from the leaf into the phloem; (h) the sensitivity of the guard cells to the [ABA] that finally reaches them; and lastly (i) the possible interaction between nitrate stress and the ABA signal.

Mitogen-activated protein kinase (MAPK) cascades have been identified in various signaling pathways involved in plant development and stress responses. We identified a drought-hypersensitive mutant (drought-hypersensitive mutant1 [dsm1]) of a putative MAPK kinase kinase (MAPKKK) gene in rice (Oryza sativa). Two allelic dsm1 mutants were more sensitive than wild-type plants to drought stress at both seedling and panicle development stages. The dsm1 mutants lost water more rapidly than wild-type plants under drought stress, which was in agreement with the increased drought-sensitivity phenotype of the mutant plants. DSM1-RNA interference lines were also hypersensitive to drought stress. The predicted DSM1 protein belongs to a B3 subgroup of plant Raf-like MAPKKKs and was localized in the nucleus. By real-time PCR analysis, the DSM1 gene was induced by salt, drought, and abscisic acid, but not by cold. Microarray analysis revealed that two peroxidase (POX) genes, POX22.3 and POX8.1, were sharply down-regulated compared to wild type, suggesting that DSM1 may be involved in reactive oxygen species (ROS) signaling. Peroxidase activity, electrolyte leakage, chlorophyll content, and 3,3′-diaminobenzidine staining revealed that the dsm1 mutant was more sensitive to oxidative stress due to an increase in ROS damage caused by the reduced POX activity. Overexpression of DSM1 in rice increased the tolerance to dehydration stress at the seedling stage. Together, these results suggest that DSM1 might be a novel MAPKKK functioning as an early signaling component in regulating responses to drought stress by regulating scavenging of ROS in rice.

MYB-type transcription factors play a diverse role in plant development and response to abiotic stress. This study isolated a rice R2R3-type MYB gene, OsMYB2, and functionally characterized its role in tolerance to abiotic stress by generating transgenic rice plants with overexpressing and RNA interference OsMYB2. Expression of OsMYB2 was up-regulated by salt, cold, and dehydration stress. OsMYB2 was localized in the nucleus with transactivation activity. No difference in growth and development between the OsMYB2-overexpressing and wild-type plants was observed under normal growth conditions, but the OsMYB2-overexpressing plants were more tolerant to salt, cold, and dehydration stresses and more sensitive to abscisic acid than wild-type plants. The OsMYB2-overexpressing plants accumulated greater amounts of soluble sugars and proline than wild-type plants under salt stress. Overexpression of OsMYB2 enhanced up-regulation of genes encoding proline synthase and transporters. The OsMYB2-overexpressing plants accumulated less amounts of H(2)O(2) and malondialdehyde. The enhanced activities of antioxidant enzymes, including peroxidase, superoxide dismutase, and catalase, may underlie the lower H(2)O(2) contents in OsMYB2-overexpressing plants. There was greater up-regulation of stress-related genes, including OsLEA3, OsRab16A, and OsDREB2A, in the OsMYB2-overexpressing plants. Microarray analysis showed that expression of numerous genes involving diverse functions in stress response was altered in the OsMYB2-overexpressing plants. These findings suggest that OsMYB2 encodes a stress-responsive MYB transcription factor that plays a regulatory role in tolerance of rice to salt, cold, and dehydration stress.

Stomatal pores located on the plant epidermis regulate CO(2) uptake for photosynthesis and the loss of water by transpiration. The opening and closing of the pore is mediated by turgor-driven volume changes of two surrounding guard cells. These highly specialized cells integrate internal signals and environmental stimuli to modulate stomatal aperture for plant survival under diverse conditions. Modulation of transcription and mRNA processing play important roles in controlling guard-cell activity, although the details of these levels of regulation remain mostly unknown. Here we report the characterization of AtMYB60, a R2R3-MYB gene of Arabidopsis, as the first transcription factor involved in the regulation of stomatal movements. AtMYB60 is specifically expressed in guard cells, and its expression is negatively modulated during drought. A null mutation in AtMYB60 results in the constitutive reduction of stomatal opening and in decreased wilting under water stress conditions. Transcript levels of a limited number of genes are altered in the mutant, and many of these genes are involved in the plant response to stress. Our data indicate that AtMYB60 is a transcriptional modulator of physiological responses in guard cells and open new possibilities to engineering stomatal activity to help plants survive desiccation.

The ABA-responsive barley gene HVA1, a member of group 3 late embryogenesis abundant (LEA) protein genes, was introduced into spring wheat (Triticum aestivum L.) cv. Hi-Line using the biolistic bombardment method. High levels of expression of the HVA1 gene, regulated by the maize ubi1 promoter, were observed in leaves and roots of independent transgenic wheat plants and were inherited by offspring generations. T(3) progenies of four selected transgenic wheat lines were tested under greenhouse conditions for tolerance of soil water deficit. Potted plants were grown under moderate water deficit and well-watered conditions, respectively. Two homozygous and one heterozygous transgenic lines expressing the HVA1 gene had significantly (P<0.01) higher water use efficiency values, 0.66-0.68 g kg(-1), as compared to 0.57 and 0.53 g kg(-1), respectively, for the non-expressing transgenic and non-transgenic controls under moderate water deficit conditions. The two homozygous transgenic plant lines also had significantly greater total dry mass, root fresh and dry weights, and shoot dry weight compared to the two controls under soil water deficit conditions. Results of this study indicate that growth characteristics were improved in transgenic wheat plants constitutively expressing the barley HVA1 gene in response to soil water deficit.

Anther culture-derived haploid embryos were used as explants for Agrobacterium-mediated genetic transformation of bread wheat (Triticum aestivum L. cv CPAN1676) using barley HVA1 gene for drought tolerance. Regenerated plantlets were checked for transgene integration in T₀ generation, and positive transgenic haploid plants were doubled by colchicine treatment. Stable transgenic doubled haploid plants were obtained, and transgene expression was monitored till T₄ generation, and no transgene silencing was observed over the generations. Doubled haploid transgenic plants have faster seed germination and seedling establishment and show better drought tolerance in comparison with nontransgenic, doubled haploid plants, as measured by per cent germination, seedling growth and biomass accumulation. Physiological evaluation for abiotic stress by assessing nitrate reductase enzyme activity and plant yield under post-anthesis water limitation revealed a better tolerance of the transgenics over the wild type. This is the first report on the production of double haploid transgenic wheat through anther culture technique in a commercial cultivar for a desirable trait. This method would also be useful in functional genomics of wheat and other allopolyploids of agronomic importance.© 2010 The Authors. Plant Biotechnology Journal © 2010 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd.

Rice (Oryza sativa L.) is an important food crop and requires larger amount of water throughout its life cycle as compared to other crops. Hence, water related stress cause severe threat to rice production. Drought is a major challenge limiting rice production. It affects rice at morphological (reduced germination, plant height, plant biomass, number of tillers, various root and leaf traits), physiological (reduced photosynthesis, transpiration, stomatal conductance, water use efficiency, relative water content, chlorophyll content, photosystem II activity, membrane stability, carbon isotope discrimination and abscisic acid content), biochemical (accumulation of osmoprotectant like proline, sugars, polyamines and antioxidants) and molecular (altered expression of genes which encode transcription factors and defence related proteins) levels and thereby affects its yield. To facilitate the selection or development of drought tolerant rice varieties, a thorough understanding of the various mechanisms that govern the yield of rice under water stress condition is a prerequisite. Thus, this review is focused mainly on recent information about the effects of drought on rice, rice responses as well as adaptation mechanisms to drought stress.

水稻是全球最重要的粮食作物之一，其生长过程需要大量水分。随着全球气候变暖，干旱成为其产量的重要限制因素。因此，本文结合近些年的研究成果从形态（根系和地上部）、生理（气孔、蒸腾作用、光合作用和水分利用率）、生化（植物激素、脯氨酸等渗透调节剂和抗氧化剂）及分子水平（抗旱基因的表达水平）综述了水稻在干旱胁迫下的自我保护机制，可为全面了解水稻抗旱机制和选育抗旱品种提供参考。

Heterologous expression of plant genes is becoming an important strategy for the improvement of specific traits in existing cultivars. This study presents the response of a salt-sensitive high-yielding wheat variety under stress-inducible expression of barley HVA1 gene belonging to the Late embryogenesis abundance (LEA) gene family. Six homozygous transgenic wheat plants were developed and advanced for testing under various water regimes and salt stress conditions. Putative transgenic plants showed better germination and root shoot development at the early developmental stages under drought stress conditions. Moreover, transgenic plants illustrated higher values of physiological features as compared to non-transgenic plants under both drought and salinity stresses that indicate improved physiological processes in transgenic plants. Higher membrane stability index (MSI) and lower electrolyte leakage (EL) after exposure to abiotic stresses reveal improved cellular membrane stability (CMS) and reduced injury to chloroplast membrane. Interestingly, under salinity stress, transgenic wheat plants showed preference towards higher K accumulation in the shoot, which is not a well-understood HVA1 mediated Na  avoidance mechanism under excessive subsurface salts. The predisposition of K/Na  under salt stress conditions on heterologous expression of the HVA1 gene in wheat needs to be studied in detail in further studies.Copyright © 2022 Elsevier Masson SAS. All rights reserved.

A single-copy barley gene, HVA1, encoding a class 3 late embryogenesis-abundant protein, can be induced by either treatment with abscisic acid (ABA) or by stress conditions such as drought, cold, heat and salinity. We have isolated an HVA1 genomic clone containing about 400 bp of 5'-upstream sequence, a single 109 bp intron, and the full coding sequence. Linker scan mutagenesis and transient expression studies were used to test the function of four HVA1 promoter elements conserved in ABA-responsive genes. Mutations in two of these elements, the C box and the putative ABRE 1 (ABA-responsive element) containing an ACGT core, resulted in no significant change in transcription level or ABA induction. In contrast, mutations of the other two elements, putative ABRE 2 & 3 cause the level of transcription to drop to 10-20% of that obtained with the wild-type promoter indicating that the high level of expression of HVA1 is dependent on both pABRE 2 & 3. Interestingly, despite their low level of expression, the mutated promoters still gave more than 20-fold induction in response to ABA treatment. We suggest that the ABA induction of barley HVA1 gene is governed by a complex consisting of pABRE 2 & 3 working together to regulate the absolute level of expression, and either of these elements or a possible third element may regulate ABA inducibility. Phylogenetic analysis by parsimony indicates that the barley HVA1 and wheat pMA2005 sequences share a recent common ancester. These two genes are closely related to the carrot Dc3 and cotton D-7 genes with which they share a similar structural gene organization.