Dynamics of auxin-dependent Ca2+ and pH signaling in root growth revealed by integrating high-resolution imaging with automated computer vision-based analysis

Plants adapt to a changing environment by entraining their growth and development to prevailing conditions. Such 'plastic' development requires a highly dynamic integration of growth phenomena with signal perception and transduction systems, such as occurs during tropic growth. The plant hormone auxin has been shown to play a key role in regulating these directional growth responses of plant organs to environmental cues. However, we are still lacking a cellular and molecular understanding of how auxin-dependent signaling cascades link stimulus perception to the rapid modulation of growth patterns. Here, we report that in root gravitropism of Arabidopsis thaliana, auxin regulates root curvature and associated apoplastic, growth-related pH changes through a Ca2+-dependent signaling pathway. Using an approach that integrates confocal microscopy and automated computer vision-based image analysis, we demonstrate highly dynamic root surface pH patterns during vertical growth and after gravistimulation. These pH dynamics are shown to be dependent on auxin, and specifically on auxin transport mediated by the auxin influx carrier AUX1 in cells of the lateral root cap and root epidermis. Our results further indicate that these pH responses require auxin-dependent changes in cytosolic Ca2+ levels that operate independently of the TIR1 auxin perception system. These results demonstrate a methodology that can be used to visualize vectorial auxin responses in a manner that can be integrated with the rapid plant growth responses to environmental stimuli.     

The interplay between light and jasmonate signalling during defence and development

During their evolution, plants have acquired diverse capabilities to sense their environment and modify their growth and development as required. The versatile utilization of solar radiation for photosynthesis as well as a signal to coordinate developmental responses to the environment is an excellent example of such a capability. Specific light quality inputs are converted to developmental outputs mainly through hormonal signalling pathways. Accordingly, extensive interactions between light and the signalling pathways of every known plant hormone have been uncovered in recent years. One such interaction that has received recent attention and forms the focus of this review occurs between light and the signalling pathway of the jasmonate hormone with roles in regulating plant defence and development. Here the recent research that revealed new mechanistic insights into how plants might integrate light and jasmonate signals to modify their growth and development, especially when defending themselves from either pests, pathogens, or encroaching neighbours, is discussed.     

Integration of local and systemic signaling pathways for plant N responses

Nitrogen (N) is an essential macronutrient and a signal that has profound impacts on plant growth and development. In order to cope with changing N regimes in the soil, plants have developed complex regulatory mechanisms that involve short-range and long-range signaling pathways. These pathways act at the cellular and whole plant scale to coordinate plant N metabolism, growth and development according to external and internal N status. Although molecular components of local and systemic N signaling have been identified and characterized, an integrated view of how plants coordinate and organize the N response is still lacking. In this review, we discuss recent advances toward understanding the mechanisms of local and systemic N responses and provide an integrated model for how these responses are orchestrated.     

Blue light sensory systems in plants

Plant development is influenced by many environmental stimuli, including light, temperature and gravity. Of these stimuli, light is of particular importance because plants depend on it for energy and, thus, for survival. Moreover, virtually all stages of plant development are regulated in part by light through the action of various photosensory systems. Examples of light-regulated processes include germination, stem growth, leaf and root development, tropic responses and flower induction. This review provides an analysis of recent investigations of blue light sensory systems in plants. Current results suggest that plants respond to blue light through a complex photosensory network that incorporates the action of multiple blue light perception systems.     

植物的环境信号分子茉莉酸及其生物学功能

茉莉酸信号分子参与植物生长发育众多生理过程的调控,尤其是作为环境信号分子能有效地介导植物对生物及非生物胁迫的防御反应。迄今已知具有信号分子生理功能的至少包括茉莉酸(jasmonic acid,JA)以及茉莉酸甲酯(methyl jasmonate,Me JA)和茉莉酸-异亮氨酸复合物(jasmonoyl-isoleucine,JA-Ile)等茉莉酸衍生物,统称为茉莉酸类化合物(jasmonates,JAs)。从环境信号分子角度介绍了茉莉酸信号的启动(环境信号感知与转导、茉莉酸类化合物合成)、传递(局部传递、维管束传输、空气传播)和生物学功能(茉莉酸信号受体、调控的转录因子、参与的生物学过程)。     

生长素通过MAPK介导的超长链脂肪酸合成调控侧根发育

促分裂原活化蛋白激酶(MAPK)信号级联通路是真核生物中高度保守的重要信号系统,通过激酶逐级磷酸化传递并放大上游信号,进而调控细胞反应。MAPK信号通路不仅介导植物响应环境变化,而且在调节植物生长发育过程中发挥重要作用。近期,山东大学丁兆军课题组研究发现,植物重要激素生长素能够通过激活MPK14调控下游ERF13的磷酸...     

Flowering responses to light and temperature

Light and temperature signals are the most important environmental cues regulating plant growth and development. Plants have evolved various strategies to prepare for, and adapt to environmental changes. Plants integrate environmental cues with endogenous signals to regulate various physiological processes, including flowering time. There are at least five distinct pathways controlling flowering in the model plant Arabidopsis thaliana: the photoperiod pathway, the vernalization/thermosensory pathway, the autonomous floral initiation, the gibberellins pathway, and the age pathway. The photoperiod and temperature/vernalization pathways mainly perceive external signals from the environment, while the autonomous and age pathways transmit endogenous cues within plants. In many plant species, floral transition is precisely controlled by light signals(photoperiod) and temperature to optimize seed production in specific environments. The molecular mechanisms by which light and temperature control flowering responses have been revealed using forward and reverse genetic approaches. Here we focus on the recent advances in research on flowering responses to light and temperature.     

Transgenic plants with altered ethylene biosynthesis or perception

The plant hormone ethylene is an essential signaling molecule involved in many plant processes including: germination, flower development, fruit ripening and responses to many environmental stimuli. Moreover, large increases in ethylene levels occur during plant stress responses, fruit ripening and flower wilting. Manipulation of ethylene biosynthesis or perception allows us to modulate these processes and thereby create plants with more robust and/or desirable traits, giving us a glimpse into the role of ethylene in the plant. Here, recent and landmark advances in genetic alteration of members of the ethylene pathway in plants and the physiological consequences of these alterations are examined.     

综述: 植物蛋白O-GlcNAc糖基化及生物学功能

蛋白质的O-GlcNAc糖基化现象发现迄今已有30多年历史．动物中,O-GlcNAc糖基化在调控细胞信号转导、基因转录、表观遗传和新陈代谢等方面发挥重要作用．而植物中,O-GlcNAc糖基化在近几年才得到关注并进行初步研究．本文对植物中O-GlcNAc修饰的糖供体合成途径、O-GlcNAc修饰关键酶、O-GlcNAc修饰蛋白的检测及功能等方面的研究工作进行归纳总结,发现O-GlcNAc糖基化在植物的生长发育、激素网络调控、信号转导、植物病毒侵染等过程均发挥重要作用,为进一步研究植物中O-GlcNAc糖基化的生物学功能提供参考．     

ICE1 CBF信号通路在植物抵御低温胁迫和调控发育过程中的作用研究进展

低温作为重要的环境因子影响着植物的地理分布和物种多样性,并且对农业可持续发展造成了严重的威胁。ICE1(INDUCER OF CBF EXPRESSION1) CBF(C REPEAT BINDING FACTOR)信号通路不仅在植物抵御低温胁迫的过程中发挥着关键作用,也在植物调控生长发育的过程中也扮演着重要角色,对ICE1 CBF调控机理的了解有助于深入认识植物如何在逆境条件下平衡生长与生存之间的关系。该文对近年来国内外有关ICE1 CBF通路在低温信号转导中的精细调控过程的研究进展进行了综述,并重点对ICE1 CBF在调控植物发育中的作用进行了讨论。     

Hormonal interactions during root tropic growth: hydrotropism versus gravitropism

Terrestrial plants have evolved remarkable morphological plasticity that enables them to adapt to their surroundings. One of the most important traits that plants have acquired is the ability to sense environmental cues and use them as a basis for governing their growth orientation. The directional growth of plant organs relative to the direction of environmental stimuli is a tropism. The Cholodny–Went theory proposes that auxin plays a key role in several tropisms. Recent molecular genetic studies have strongly supported this hypothesis for gravitropism. However, the molecular mechanisms of other tropisms are far less clear. Hydrotropism is the response of roots to a moisture gradient. Since its re-discovery in 1985, root hydrotropism has been shown to be common among higher plant species. Additionally, in some species, gravitropism interferes with hydrotropism, suggesting that both shared and divergent mechanisms mediating the two tropisms exist. This hypothesis has been supported by recent studies, which provide an understanding of how roots sense multiple environmental cues and exhibit different tropic responses. In this review, we focus on the overlapping and unique mechanisms of the hormonal regulation underlying gravitropism and hydrotropism in roots.     

New perspectives on plant defense responses through modulation of developmental pathways

Invasion mechanisms of pathogens and counteracting defense mechanisms of plants are highly diverse and perpetually evolving. While most classical studies of plant defense have focused only on defense-specific factor-mediated responses, recent work is beginning to shed light on the involvement of non-stress signal components, especially growth and developmental processes. This shift in focus links plant resistance more closely with growth and development. In this review, we summarize our current understanding of how pathogens manipulate host developmental processes and, conversely, of how plants deploy their developmental processes for self-protection. We conclude by introducing our recent work on UNI, a novel R protein in Arabidopsis which mediates cross-talk between developmental processes and defense responses.     

An update on the function and regulation of methylerythritol phosphate and mevalonate pathways and their evolutionary dynamics

Isoprenoids are among the largest and most chemically diverse classes of organic compounds in nature and are involved in the processes of photosynthesis, respiration, growth, development, and plant responses to stress. The basic building block units for isoprenoid synthesis—isopentenyl diphosphate and its isomer dimethylallyl diphosphate—are generated by the mevalonate (MVA) and methylerythritol phosphate (MEP) pathways. Here, we summarize recent advances on the roles of the MEP and MVA pathways in plant growth, development and stress responses, and attempt to define the underlying gene networks that orchestrate the MEP and MVA pathways in response to developmental or environmental cues. Through phylogenomic analysis, we also provide a new perspective on the evolution of the plant isoprenoid pathway. We conclude that the presence of the MVA pathway in plants may be associated with the transition from aquatic to subaerial and terrestrial environments, as lineages for its core components are absent in green algae. The emergence of the MVA pathway has acted as a key evolutionary event in plants that facilitated land colonization and subsequent embryo development, as well as adaptation to new and varied environments.     

Maintenance of meristem activity under stress: is there an interplay of RSS1‐like proteins with the RBR pathway?

Plants have acquired rapid responses to a constantly changing environment. These adaptive and protective responses are the result of a complex signalling network regulating different aspects, ranging from ion homeostasis to cell cycle control. It is well established that stress inhibits cell division, which negatively impacts plant growth and development and hence results in biomass decrease and yield loss. Therefore understanding the link between stress perception and cell cycle control would allow development of new crops with increased productivity when subjected to stress. However, studies on cell cycle control under stress have been limited to well‐known regulators of the cell cycle such as cyclins and stress‐related phytohormone integrators. The recent discovery of RSS1, a novel intrinsically unstructured protein of rice, opened up new insights into how stress perception can be connected with cell cycle control in meristematic zones. Whereas RSS1 is well conserved among other plant lineages, eudicots present proteins sharing little sequence homology with RSS1. Here, we discuss how RSS1‐like proteins might also be functional in dicots, and possibly act through the retinoblastoma‐related pathway to regulate both S‐phase transition and cell fate in meristems.     

The role of ethylene in plant temperature stress response

Temperature influences the seasonal growth and geographical distribution of plants. Heat or cold stress occur when temperatures exceed or fall below the physiological optimum ranges, resulting in detrimental and irreversible damage to plant growth, development, and yield. Ethylene is a gaseous phytohormone with an important role in plant development and multiple stress responses. Recent studies have shown that, in many plant species, both heat and cold stress affect ethylene biosynthesis and signaling pathways. In this review, we summarize recent advances in understanding the role of ethylene in plant temperature stress responses and its crosstalk with other phytohormones. We also discuss potential strategies and knowledge gaps that need to be adopted and filled to develop temperature stress-tolerant crops by optimizing ethylene response.     

Soil-mediated indirect impacts of an invasive predator on plant growth

While several studies have shown that invasive plant effects on soil biota influence subsequent plant performance, corresponding studies on how invasive animals affect plants through influencing soil biota are lacking. This is despite the fact that invasive animals often indirectly alter the below-ground subsystem. We studied 18 offshore islands in northern New Zealand, half of which have been invaded by rats that are predators of seabirds and severely reduce their densities, and half of which remain non-invaded; invasion of rats thwarts seabird transfer of resources from ocean to land. We used soil from each island in a glasshouse experiment involving soil sterilization treatments to determine whether rat invasion indirectly influences plant growth through the abiotic pathway (by impairing seabird-driven inputs to soil) or the biotic pathway (by altering the soil community). Rat invasion greatly impaired plant growth but entirely through the abiotic pathway. Plant growth was unaffected by the soil community or its response to invasion, meaning that the responses of plants and soil biota to invasion are decoupled. Our results provide experimental evidence for the powerful indirect effects that predator-instigated cascades can exert on plant and ecosystem productivity, with implications for the restoration of island ecosystems by predator removal.