Enzyme immunoassay of (24R)-brassinosteroids

Brassinosteroids are a new group of phytohormones that are widely distributed in plants and play an important role in the processes of plant growth and development. Physiological concentrations of brassinosteroids in plants are extremely low, and their analysis in organs and tissues is very difficult. This study is devoted to the chemical aspects of elaboration and to bioanalytical parameters of an immunoenzymatic system for quantitative determination of the phytohormones 24-epicastasterone and 24-epibrassinolide.     

Brassinosteroids promote root growth in Arabidopsis

Although brassinosteroids (BRs) are known to regulate shoot growth, their role in the regulation of root growth is less clear. We show that low concentrations of BRs such as 24-epicastasterone and 24-epibrassinolide promote root elongation in Arabidopsis wild-type plants up to 50% and in BR-deficient mutants such as dwf1-6 (cbb1) and cbb3 (which is allelic to cpd) up to 150%. The growth-stimulating effect of exogenous BRs is not reduced by the auxin transport inhibitor 2,3,5-triidobenzoic acid. BR-deficient mutants show normal gravitropism, and 2,3,5-triidobenzoic acid or higher concentrations of 2,4-dichlorophenoxyacetic acid and naphtaleneacetic acid inhibit root growth in the mutants to the same extent as in wild-type plants. Simultaneous administration of 24-epibrassinolide and 2,4-dichlorophenoxyacetic acid results in largely additive effects. Exogenous gibberellins do not promote root elongation in the BR-deficient mutants, and the sensitivity to the ethylene precursor 1-aminocyclopropane-1-carboxylic acid is not altered. Thus, the root growth-stimulating effect of BRs appears to be largely independent of auxin and gibberellin action. Furthermore, we analyzed BR interactions with other phytohormones on the gene expression level. Only a limited set of auxin- and ethylene-related genes showed altered expression levels. Genes related to other phytohormones barely showed changes, providing further evidence for an autonomous stimulatory effect of BR on root growth.     

Phytohormone Priming: Regulator for Heavy Metal Stress in Plants

Phytohormones act as chemical messengers and, under a complex regulation, allow plants to sustain biotic and abiotic stresses. Thus, phytohormones are known for their regulatory role in plant growth and development. Heavy metals (HMs) play an important role in metabolism and have roles in plant growth and development as micronutrients. However, at a level above threshold, these HMs act as contaminants and pose a worldwide environmental threat. Thus, finding eco-friendly and economical deliverables to tackle this problem is a priority. In addition to physicochemical methods, exogenous application of phytohormones, i.e., auxins, cytokinins, and gibberellins, can positively influence the regulation of the ascorbate–glutathione cycle, transpiration rate, cell division, and the activities of nitrogen metabolism and assimilation, which improve plant growth activity. Brassinosteroids, ethylene and salicylic acid have been reported to enhance the level of the anti-oxidant system, decrease levels of ROS, lipid peroxidation and improve photosynthesis in plants, when applied exogenously under a HM effect. There is a crosstalk between phytohormones which is activated upon exogenous application. Research suggests that plants are primed by phytohormones for stress tolerance. Chemical priming has provided good results in plant physiology and stress adaptation, and phytohormone priming is underway. We have reviewed promising phytohormones, which can potentially confer enhanced tolerance when used exogenously. Exogenous application of phytohormones may increase plant performance under HM stress and can be used for agro-ecological benefits under environmental conditions with high HMs level.

     

The role of phytohormone signaling in ozone-induced cell death in plants

Ozone is the main photochemical oxidant that causes leaf damage in many plant species, and can thereby significantly decrease the productivity of crops and forests. When ozone is incorporated into plants, it produces reactive oxygen species (ROS), such as superoxide radicals and hydrogen peroxide. These ROS induce the synthesis of several plant hormones, such as ethylene, salicylic acid, and jasmonic acid. These phytohormones are required for plant growth, development, and defense responses, and regulate the extent of leaf injury in ozone-fumigated plants. Recently, responses to ozone have been studied using genetically modified plants and mutants with altered hormone levels or signaling pathways. These researches have clarified the roles of phytohormones and the complexity of their signaling pathways. The present paper reviews the biosynthesis of the phytohormones ethylene, salicylic acid, and jasmonic acid, their roles in plant responses to ozone, and multiple interactions between these phytohormones in ozone-exposed plants.Key words: cross-talk, ethylene, jasmonic acid, ozone, phytohormones, programmed cell death, salicylic acid, signaling pathways     

Plant nitrogen availability and crosstalk with phytohormones signallings and their biotechnology breeding application in crops

Nitrogen (N), one of the most important nutrients, limits plant growth and crop yields in sustainable agriculture system, in which phytohormones are known to play essential roles in N availability. Hence, it is not surprising that massive studies about the crosstalk between N and phytohormones have been constantly emerging. In this review, with the intellectual landscape of N and phytohormones crosstalk provided by the bibliometric analysis, we trace the research story of best-known crosstalk between N and various phytohormones over the last 20 years. Then, we discuss how N regulates various phytohormones biosynthesis and transport in plants. In reverse, we also summarize how phytohormones signallings modulate root system architecture (RSA) in response to N availability. Besides, we expand to outline how phytohormones signallings regulate uptake, transport, and assimilation of N in plants. Further, we conclude advanced biotechnology strategies, explain their application, and provide potential phytohormones-regulated N use efficiency (NUE) targets in crops. Collectively, this review provides not only a better understanding on the recent progress of crosstalk between N and phytohormones, but also targeted strategies for improvement of NUE to increase crop yields in future biotechnology breeding of crops.     

水稻根分泌激素调节生长速度

植物激素是植物体内合成的一类重要小分子物质,其含量可因外界条件变化而改变,并作为信号物质调控植物生长发育和适应环境。水培所用介质体积过小会造成植物生长受限、植株矮小,通常认为是小体积生长介质中营养成分不足所致。研究表明,在不同体积且不含任何营养物质的纯水中培养的水稻(Oryza sativa)亦表现出不同的生长速度,幼...     

Phytohormones and rice crop yield: strategies and opportunities for genetic improvement

To feed an estimated world population of 8.9 billion by 2050, strategies for increasing grain production must be developed. Several agronomically important traits for increasing yield, such as plant height, grain number, and leaf erectness, have recently been characterized in rice (Oryza sativa L.). These traits are regulated primarily by three phytohormones: gibberellins, cytokinins, and brassinosteroids. The control of biosynthesis and degradation of these key phytohormones is discussed in terms of its importance for normal plant growth. Genes involved in the biosynthesis and regulation of these phytohormones can be used to develop effective strategies to increase grain yield. Genetic manipulation of phytohormone-related gene expression is thus a practical strategy to generate high-yielding transgenic plants through the modification of levels and profile of endogenous phytohormones.     

Strigolactones in plant adaptation to abiotic stresses: An emerging avenue of plant research

Phytohormones play central roles in boosting plant tolerance to environmental stresses, which negatively affect plant productivity and threaten future food security. Strigolactones (SLs), a class of carotenoid‐derived phytohormones, were initially discovered as an “ecological signal” for parasitic seed germination and establishment of symbiotic relationship between plants and beneficial microbes. Subsequent characterizations have described their functional roles in various developmental processes, including root development, shoot branching, reproductive development, and leaf senescence. SLs have recently drawn much attention due to their essential roles in the regulation of various physiological and molecular processes during the adaptation of plants to abiotic stresses. Reports suggest that the production of SLs in plants is strictly regulated and dependent on the type of stresses that plants confront at various stages of development. Recently, evidence for crosstalk between SLs and other phytohormones, such as abscisic acid, in responses to abiotic stresses suggests that SLs actively participate within regulatory networks of plant stress adaptation that are governed by phytohormones. Moreover, the prospective roles of SLs in the management of plant growth and development under adverse environmental conditions have been suggested. In this review, we provide a comprehensive discussion pertaining to SL‐mediated plant responses and adaptation to abiotic stresses.     

NO在植物生长发育和环境胁迫响应中的作用

一氧化氮(NO)是具有生物活性和信号转导作用的气体活性分子,它不仅对植物的许多生命活动如种子萌发、生长和衰老等具有直接的生理调节功能,而且作为防御反应中的关键信使,参与了植物对外界环境胁迫的响应,如干旱胁迫、热胁迫、盐胁迫、UV-B辐射、臭氧胁迫、重金属胁迫、机械损伤以及植物抗病反应。NO与各种激素如乙烯、脱落酸、水杨酸、生长素和细胞分裂素等,在调节植物的生理活动与信号转导方面有明显的协同作用,通过激素起作用可能是植物内源NO作用的机理之一。探明在正常生长状况下植物内源NO对植物生长发育的调控机制及其参与信号转导的生理机制是目前研究的重点。     

Role of Phytohormones in Sex Differentiation in Plants

The role of phytohormones in sex expression in plants is briefly surveyed. The interaction of hereditary and environmental factors in sex expression is considered. A major role of gibberellins and cytokinins in the regulation of sex expression in dioecious and monoecious flowering plants and in some muscoids is demonstrated. The evidence for the effect of other phytohormones and physiologically active compounds on sex expression in plants is examined.     

Participation of Phytohormones in the Stomatal Regulation of Gas Exchange During Water Stress

Almost all processes in the life of a plant are directly or indirectly affected by both stresses and phytohormones. Nevertheless, apart from abscisic acid, the role of phytohormones in plant response to water stress is far from being fully elucidated. This review tries to answer the question whether interactions between abscisic acid and some other phytohormones might be important in the regulation of stomatal opening during water stress and subsequent rehydration. Firstly, it describes the changes in the contents of individual endogenous phytohormones during water stress. Then, it deals with the effects of applied phytohormones on stomatal opening, and on transpiration and photosynthetic rates in different plants species. Finally, it focuses on the alleviation or stimulation of absicic acid-induced stomatal closure by application of other phytohormones. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sensitivity to phytohormones determined by outer-inner polarity of higher plants: An overall model for phytohormone action

Abstract A generalized model of the higher plant body is proposed in order to assemble the discrete knowledge of the actions, and sites of biosynthesis, of phytohormones. In this model, we attempt to explain the differential sensitivities of different tissues. With this model most effects of plant hormones appear to be reasonable, and even expected. The model is based on a new anatomical and physiological classification of plant tissue. In higher plants the integration of an outer-inner polarity and an upper-lower polarity plays a major role in phytohormone behaviour. Plant tissues and organs which are derived from the cortex of paleophytes (the bud, the mesophyll of the leaf, the cortex of the stem, and the root cap) are classified as the outer pole of the plant. On the other hand, tissues and organs which are derived from the stele of paleophytes (the root, the stele of the shoot, and the vein of the leaf), are classified as the inner pole. It is suggested that tissue sensitivities to phytohormones are mainly determined by the outer-inner polarity. Phytohormones which are synthesized from one pole act on the other, whereas they exert either much less or no effect, or an inverse effect on their own pole. This is shown for both promoters and inhibitors of the phytohormones for both cortical and stelar vegetative tissues of plants.     

Gibberellin and Jasmonate Crosstalk during Stamen Development

Gibberellin (GA) and jasmonate (JA) are two types of phytohormones that play important roles during stamen development. For example, Arabidopsis plants deficient in either of GA or JA develop short stamens. An apparent question to ask is whether GA action and JA action during stamen filament development are independent of each other or are in a hierarchy. Recent studies showed that GA modulates the expression of genes essential for JA biosynthesis to promote JA production and high levels of JA will induce the expression of three MYB genes MYB21, MYB24 and MYB57. These three MYB genes are crucial factors for the normal development of stamen filament in Arabidopsis.     

Control of plant organ size by KLUH/CYP78A5-dependent intercellular signaling

Plant organs grow to characteristic sizes that are genetically controlled. In animals, signaling by mobile growth factors is thought to be an effective mechanism for measuring primordium size, yet how plants gauge organ size is unclear. Here, we identify the Arabidopsis cytochrome P450 KLUH (KLU)/CYP78A5 as a stimulator of plant organ growth. While klu loss-of-function mutants form smaller organs because of a premature arrest of cell proliferation, KLU overexpression leads to larger organs with more cells. KLU promotes organ growth in a non-cell-autonomous manner, yet it does not appear to modulate the levels of known phytohormones. We therefore propose that KLU is involved in generating a mobile growth signal distinct from the classical phytohormones. The expression dynamics of KLU suggest a model of how the arrest of cell proliferation is coupled to the attainment of a certain primordium size, implying a common principle of size measurement in plants and animals.     

Phytohormones Accumulation and Distribution in Shoots and Roots of Haploid,Diploid and Tetraploid Barley Seedlings Derived from Microspore Culture

Phytohormones play important roles in plant growth and development, and polyploids are thought to be an important method for plant breeding. However, the relationship between ploidy and phytohormone is still unclear. In this study, barley at three ploidy levels were produced by microspore culture. Therefore, we further analyzed the phytohormone content in the shoots and roots of the three kinds of barley materials to study the effect of ploidy on phytohormones accumulation and distribution. The results showed that Abscisic acid (ABA), gibberellin (GA), jasmonic acid (JA), auxin (IAA), salicylic acid (SA) and cytokinin (CTK) were successfully determined in shoots and roots using LC-MS (liquid chromatography mass spectrometry). By comparing the shoots of the haploid and diploid plants, it was found that the distribution trend of the six phytohormones was consistent, and another consistent trend was found in the roots of the diploid and tetraploid plants. In addition, we further analyzed the shoot/root ratio of the different phytohormones to identify the potential differences for haploid, diploid and tetraploid. Here, the relationship between ploidy and phytohormone we provided would provide new insights into understanding the new phenotypes that occur in polyploid species.     

Plant Growth-Promoting Rhizobacteria-Mediated Adaptive Responses of Plants Under Salinity Stress

In this recent era, several approaches have been developed to alleviate the adverse effects of salinity stress in different plants. However, some of them are not eco-friendly. In this context, evolving sustainable approaches which enhance the productivity of saline soil without harming the environment are necessary. Many recent studies showed that plant growth-promoting rhizobacteria (PGPR) are known to confer salinity tolerance to plants. Salt-stressed plants inoculated with PGPR enhance the growth and productivity of crops by reducing oxidative damage, maintaining ionic homeostasis, enhancing antioxidant machinery, and regulating gene expressions. The PGPR also regulates the photosynthetic attributes such as net photosynthetic rate, chlorophyll, and carotenoid contents and enhances the salinity tolerance to plants. Moreover, PGPR has a great role in the enhancement of phytohormones and secondary metabolites synthesis in plants under salt stress. This review summarizes the current reports of the application of PGPR in plants under salt stress and discusses the PGPR-mediated mechanisms in plants of salt tolerance. This review also discusses the potential role of PGPR in cross-talk with phytohormones and secondary metabolites to alleviate salt stress and highlights the research gaps where further research is needed.

     

Biochar Increased Plant Growth-Promoting Hormones and Helped to Alleviates Salt Stress in Common Bean Seedlings

Journal of Plant Growth Regulation - Salinity seriously disrupts the growth and physiology of plants, whereas phytohormones play an important role in regulating plant responses to salinity stress....