ABSTRACT
Alguns hormônios vegetais são amplamente conhecidos pela atuação em rotas me-tabólicas, sendo responsáveis pela promoção ou inibição do crescimento e desenvolvimento das plantas. Os brassinosteróides (BRs), recentemente incluso na classe de hormônios vegetais, são substâncias esteróides que foram inicialmente identificadas em Brassica napus, na década de 1960. Apesar de serem produzidos em pequenas quantidades pelas plantas, uma das principais características que faci-lita o modo de ação deste hormônio é a capacidade de difusão nas células. A fácil mobilidade através das membranas celulares gera resposta rápida no metabolismo das plantas, bem como no estímulo da produção de proteínas e enzimas. Os estudos acerca dos BRs estão elucidando suas diferentes funçõesno metabolismo vegetal, principalmente em relação à promoção e biossíntese de etileno, crescimento e desen-volvimento do sistema radicular, controle de estresses abióticos, ocasionados pela redução da disponibilidade de água, salinidade e temperatura, controle contra o ata-que de insetos e demais fatores bióticos, síntese de ácidos nucléicos e proteínas, regulação na germinação e a interação com outros hormônios vegetais. Diante do exposto, o objetivo desta revisão é apresentar o modo de ação deste hormôniovege-tal, os efeitos das interações com outros hormônios e as recentes descobertas das importantes contribuições para o desenvolvimento das plantas.(AU)
Some plant hormones are widely known to act on metabolic pathways and are respon-sible for promoting or inhibiting plantsgrowth and development. Brassinosteroids (BRs), recently categorized asplant hormones, are steroid substances that were ini-tially identified in Brassica napusin the 1960s. Although BRs are produced in small quantities by plants, one of the main characteristics that facilitates the mode of action of thesehormonesis theirability to spread in cells. The easy mobility through the cell membranes generates a rapid response in the metabolism of plants, as well as in the production of proteins and enzymes. The studies on BRs are elucidating their different functions in plant metabolism, especially related tothe promotion and biosynthesis of ethylene, growth and development of the root systemand control of abiotic stresses, caused by reduced availability of water, salinity and temperature. Furthermore, BRs seems to be involved in control of insect attack and other biotic factors, synthesis of nucleic acids and proteins, regulation in germination, and interaction with other plant hormones. Thus, this review aims to reportthe mode of action of Brassinosteroids, the effects of their interactions with other hormones and recent findings of important con-tributions to plant development.(AU)
Subject(s)
Plant Growth Regulators/analysis , Brassinosteroids/analysis , Brassinosteroids/adverse effectsABSTRACT
Iron is an essential plant micronutrient. It is a component of numerous proteins and participates in cell redox reactions; iron deficiency results in a reduction in nutritional quality and crop yields. Volatiles from the rhizobacterium Arthrobacter agilis UMCV2 induce iron acquisition mechanisms in plants. However, it is not known whether microbial volatiles modulate other metabolic plant stress responses to reduce the negative effect of iron deficiency. Mass spectrometry has great potential to analyze metabolite alterations in plants exposed to biotic and abiotic factors. Direct liquid introduction-electrospray-mass spectrometry was used to study the metabolite profile in Medicago truncatula due to iron deficiency, and in response to microbial volatiles. The putatively identified compounds belonged to different classes, including pigments, terpenes, flavonoids, and brassinosteroids, which have been associated with defense responses against abiotic stress. Notably, the levels of these compounds increased in the presence of the rhizobacterium. In particular, the analysis of brassinolide by gas chromatography in tandem with mass spectrometry showed that the phytohormone increased ten times in plants grown under iron-deficient growth conditions and exposed to microbial volatiles. In this mass spectrometry-based study, we provide new evidence on the role of A. agilis UMCV2 in the modulation of certain compounds involved in stress tolerance in M. truncatula.
Subject(s)
Arthrobacter/metabolism , Brassinosteroids/metabolism , Iron/metabolism , Medicago truncatula/metabolism , Spectrometry, Mass, Electrospray Ionization/methods , Volatile Organic Compounds/pharmacology , Agricultural Inoculants , Brassinosteroids/analysis , Cluster Analysis , Medicago truncatula/drug effects , Medicago truncatula/growth & development , Models, Biological , Seedlings/drug effects , Seedlings/growth & development , Seedlings/metabolism , Stress, PhysiologicalABSTRACT
Recent studies have shown that low concentrations of brassinolide induce a rapid generation of nitric oxide in mesophyll cells of maize leaves, which can be easily detected by fluorimetric methods. In this work we describe a series of natural and synthetic brassinosteroids that are able to trigger in vitro NO production in tomato cells that exhibits dose-response behavior. We propose that this effect can be used to develop a new rapid and very sensitive bioassay for brassinosteroid activity that offers several advantages when compared to the current methodologies.