CDPK-mediated abiotic stress signaling

Calcium-dependent protein kinases (CDPKs) constitute a large multigene family in various plant species. CDPKs have been shown to have important roles in various physiological processes, including plant growth and development and abiotic and biotic stress responses in plants. Functional analysis using gain-of-function and loss-of-function mutants has revealed the biological function of CDPKs in planta. Several CDPKs have been shown to be essential factors in abiotic stress tolerance, positively or negatively regulating stress tolerance by modulating ABA signaling and reducing the accumulation of reactive oxygen species (ROS). This review summarizes recent results describing the biological function of CDPKs that are involved in abiotic stress tolerance.     

In vivo role of Arabidopsis arginase in arginine metabolism and abiotic stress response

Nitric oxide (NO) and polyamines play essential roles in many developmental processes and abiotic stress responses in plants. NO and polyamines are metabolized from arginine through NO synthase (NOS) and arginine decarboxylase (ADC), respectively. Function of arginase, another important enzyme involved in arginine metabolism, in abiotic stress remains largely unknown. In the recent study, we have dissected the impact of arginase on arginine metabolism and abiotic stress responses through manipulating AtARGAHs expression. The results suggested that manipulation of arginase expression modulated accumulation of arginine and direct downstream products of arginine catabolism. AtARGAHs knockout lines exhibited increased accumulation of polyamines and NO and enhanced abiotic stress tolerance, while AtARGAHs overexpressing lines displayed the opposite results. Notably, we highlighted that Arabidopsis arginase plays distinctive and dual roles in the crosstalk between polyamines and NO signaling during abiotic stress responses, mediating both arginine metabolism and reactive oxygen species (ROS) accumulation. It is likely that accumulation of both NO and polyamines might activate abiotic stress responses in the plant.     

Nitric oxide production in tobacco leaf cells: a generalized stress response?

The function of nitric oxide (NO), a gaseous free radical emitted by many plants, is incompletely understood. In the present study the hypothesis that NO generation, like that of the reactive oxygen species, occurs as a general response to different environmental cues was tested. Leaf peels and mesophyll cell suspensions of Nicotiana tabacum cv. Xanthi were loaded with the NO‐specific fluorophore, diaminofluorescein, and subjected to an abiotic stressor. Light stress and mechanical injury had no apparent effect on NO production. In contrast, high temperatures, hyperosmotic stress, salinity and epi‐illumination in a microscope all led to rapid surges in NO‐induced fluorescence. The fluorescence originated from cells of the palisade mesophyll and across all epidermal cell types, including guard cells, subsidiary cells, and long and short trichomes. Fluorescence was evident first in the plastids, then in the nucleus and finally throughout the cytosol. Nicotiana plumbaginifolia cell suspensions expressing the calcium reporter aequorin provided evidence that, under hyperosmotic stress, NO participates in the elevation of free Ca²⁺ in the cytoplasm. The physiological significance of NO production in response to abiotic stressors is discussed.     

Modulation of ROS production and hormone levels by AHK5 during abiotic and biotic stress signaling

Histidine kinases have been shown to mediate responses to endogenous and exogenous stimuli in organisms such as yeast, bacteria and plants. In the model plant Arabidopsis, histidine kinases have been shown to function in hormone signaling, and abiotic and biotic stress responses. More recently, the least characterized of the Arabidopsis histidine kinases, AHK5, was demonstrated to function in resistance toward the virulent bacterium Pseudomonas syringae pv tomato DC3000 (PstDC3000) and the necrotrophic fungus Botrytis cinerea, and as a negative regulator of tolerance toward salinity. Here, we present data which indicate that AHK5 also impacts on drought stress resistance and on the outcome of an incompatible interaction with avrRpm1-expressing PstDC3000 (PstDC3000 (avrRpm1)). We present a model which proposes a role for reactive oxygen species (ROS) and hormones in integrating abiotic and biotic stress responses via AHK5.     

蔬菜种子萌发的纳米调控及其机制研究进展

提高种子在非生物胁迫下的萌发率可降低环境恶化对蔬菜安全构成的风险;为全球蔬菜产量提供保障。由于纳米材料具有尺寸小和独特的物理化学性质;在蔬菜生产中可应用于种子引发。纳米引发在改善非生物胁迫下蔬菜种子的萌发方面显示了突出作用。论文将用于调控蔬菜种子萌发的纳米材料分为碳基、硅基、金属颗粒和金属氧化物四类;并列举了部分纳米材料促进蔬菜种子萌发的适宜浓度。描述了不同种类纳米材料常用的合成方法及其影响因素;并比较了传统合成与绿色合成的利弊。重点综述了纳米引发对蔬菜种子和幼苗生理生化指标的影响并归纳为两种调控途径。纳米材料调控种子对水分和养分的吸收以及赤霉素合成等与萌发相关过程;从而促进萌发称为直接调控。间接调控是纳米材料产生活性氧;通过信号传导激活抗氧化系统;提高种子对非生物胁迫的抵抗力从而促进萌发。最后;阐述了纳米材料在种子中的应用;并对纳米引发未来的研究方向进行展望:（1）着重考虑纳米材料在长期条件下对环境的潜在风险;避免经过食物链对人类健康造成不利影响;（2）评估纳米材料在多种非生物胁迫下调节活性氧、保障种子萌发的性能;（3）探索由纳米材料引发产生的活性氧通过信号传导激活防御途径的整体通路;（4）补充纳米材料进入种子的准确机制。