homobrassinolide and brassinolide

Brassinolide and related brassinosteroids are a novel group of steroids which appear to be ubiquitous in plants. There is compelling evidence, particularly from recent genetic studies, that these steroids are essential for normal plant growth and development. Synthesis of brassinosteroids and aspects of their biochemistry are reviewed.

Topics: Brassinosteroids; Cholestanols; Cholestanones; Gene Expression Regulation, Plant; Molecular Structure; Plant Development; Plant Growth Regulators; Plant Physiological Phenomena; Plants; Steroids, Heterocyclic

BRs are polyhydroxylated sterol derivatives, classified as phytohormones. Plants of Brassica juncea var. Varuna were grown in pots and an aqueous solution (10

Topics: Antioxidants; Brassinosteroids; Cholestanones; Hydrogen Peroxide; Microscopy, Electron, Scanning; Mustard Plant; Photosynthesis; Photosystem II Protein Complex; Plant Growth Regulators; Plant Leaves; Plant Roots; Plant Stomata; Plant Transpiration; Steroids, Heterocyclic; Superoxides

Brassinosteroids (BRs) have been implicated to overcome various abiotic stresses, and low temperature stress poses a serious threat to productivity of various horticultural crops like tomato. Therefore, a study was conducted to unravel the possible role of BRs in conferring alleviation to low temperature stress in Lycopersicon esculentum. Twenty-day-old seedlings of tomato var. S-22 (chilling tolerant) and PKM-1 (chilling sensitive) were sown in earthen pots, and at 40 days stage of growth, plants were exposed to varied levels of low temperatures (10/3, 12/7, 20/14, or 25/18 °C) for 24 h in a growth chamber. At 50 days stage of growth, the foliage of plants were sprayed with 0 or 10(-8) M of BRs (28-homobrassinolide or 24-epibrassinolide), and 60-day-old plants were harvested to assess various physiological and biochemical parameters. Low temperatures induced a significant reduction in growth traits, chlorophyll content, and rate of photosynthesis in both the varieties differentially. Activities of antioxidant enzymes (catalase, peroxidase, and superoxide dismutase) and leaf proline content also increased substantially in both the varieties with decreasing temperature. On the other hand, treatment of BRs under stress and stress-free conditions significantly increased the aforesaid growth traits and biochemical parameters. Moreover, BRs further accelerated the antioxidative enzymes and proline content, which were already enhanced by the low temperature stress. Out of the two analogues of BRs tested, 24-epibrassinolide (EBL) was found more effective for both the varieties of tomato. EBL was found more potent stress alleviator against low temperature in both varieties of tomato.

Topics: Antioxidants; Brassinosteroids; Chlorophyll; Cholestanones; Cold-Shock Response; Photosynthesis; Plant Leaves; Seedlings; Solanum lycopersicum; Steroids, Heterocyclic

Brassinosteroids (BRs) play a vital role in plant growth, stress tolerance and productivity. Here, the involvement of BRs in the regulation of CO(2) assimilation and cellular redox homeostasis was studied. The effects of BRs on CO(2) assimilation were studied in cucumber (Cucumis sativus) through the analysis of the accumulation of H(2)O(2) and glutathione and photosynthesis-related enzyme activities using histochemical and cytochemical detection or a spectrophotometric assay, and Rubisco activase (RCA) using western blot analysis and immunogold labeling. Exogenous BR increased apoplastic H(2)O(2) accumulation, the ratio of reduced to oxidized glutathione (GSH:GSSG) and CO(2) assimilation, whereas a BR biosynthetic inhibitor had the opposite effects. BR-induced CO(2) assimilation was decreased by a H(2)O(2) scavenger or inhibition of H(2)O(2) generation, GSH biosynthesis and the NADPH-generating pentose phosphate pathway. BR-, H(2)O(2) - or GSH-induced CO(2) assimilation was associated with increased activity of enzymes in the Benson-Calvin cycle. Immunogold labeling and western blotting showed that BR increased the content of RCA and this effect was blocked by inhibitors of redox homeostasis. These results strongly suggest that BR-induced photosynthesis involves an H(2)O(2) -mediated increase in the GSH:GSSG ratio, which may positively regulate the synthesis and activation of redox-sensitive enzymes in carbon fixation.

Topics: Brassinosteroids; Carbon Dioxide; Cholestanones; Cucumis sativus; Glutathione; Homeostasis; Hydrogen Peroxide; Oxidation-Reduction; Photosynthesis; Plant Growth Regulators; Steroids, Heterocyclic

The present study was conducted with an aim to gain better insight of brassinosteroid generated response on the effects of cadmium on photosynthetic machinery and active oxygen metabolism in two tomato cultivars (K-25 and Sarvodya). These tomato cultivars were subjected to graded cadmium levels in soil (0, 3, 6, 9 or 12 mg kg(-1) soil) with their foliage being sprayed with 0 or 10(-8) M of 28-homobrassinolide/24-epibrassinolide (HBL/EBL) at 59 d stage. The results suggested that photosynthetic parameters, leaf water potential and activity of several enzymes (nitrate reductase and carbonic anhydrase) decreased significantly in both the cultivars, to a lesser extent in K-25 than Sarvodya with the increasing levels of cadmium in the soil. However, the activity of antioxidant enzymes and proline content increased in response to metal treatment as well as the application of brassinosteroids (HBL/EBL). Overall, exogenous application of brassinosteroids improved the activity of photosynthetic machinery and that of antioxidant defense system in both the cultivars, and also nullified the damaging effect of metal on these parameters.

Topics: Antioxidants; Brassinosteroids; Cadmium; Cholestanones; Oxidative Stress; Photosynthesis; Soil Pollutants; Solanum lycopersicum; Steroids, Heterocyclic

Surface-sterilized seeds of two tomato cultivars (cv. K-25 and Sarvodya) were soaked in 100 microM CdCl(2) for 8 h (shotgun approach). The resulting 59-day-old seedlings were sprayed with 10(-8) M of 28-homobrassinolide (HBL) or 24-epibrassinolide (EBL) to their foliage. Both cultivars showed significantly different response to Cd stress. Cadmium severely restricted the growth, photosynthetic efficiency, and activity of nitrate reductase (E.C. 1.6.6.1) and carbonic anhydrase (E.C. 4.2.1.1) in Sarvodya as compared to K-25. However, the activities of antioxidative enzymes were significantly higher in K-25. This result may be considered an indication of better tolerance of the K-25 cultivars to Cd stress. Moreover, the spray of both the brassinosteroids (HBL/EBL) were found very effective in neutralizing the adverse effects generated by metals that reflect in better photosynthetic performance by the cultivars. An interesting aspect of this study is that HBL or EBL spray caused a further increase in proline content and antioxidative enzyme activities, which were already enhanced by Cd stress. This effect of brassinosteroids (HBL/EBL) was more pronounced in K-25 than in Sarvodya, representing the tolerance and adoptable behavior of K-25.

Topics: Antioxidants; Ascorbic Acid; beta Carotene; Brassinosteroids; Cadmium; Carotenoids; Cholestanols; Cholestanones; Lycopene; Nitrate Reductase; Photosynthesis; Plant Growth Regulators; Plant Proteins; Proline; Seedlings; Seeds; Soil Pollutants; Solanum lycopersicum; Steroids, Heterocyclic; Vitamins