Plant hormones through signaling networks mutually regulate several signaling and metabolic systems essential for both plant development and plant responses to different environmental stresses. Extensive research has enabled the main effects of all known phytohormones classes to be identified. Therefore, it is now possible to investigate the interesting topic of plant hormonal crosstalk more fully. In this review, we focus on the role of brassinosteroids and ethylene during plant growth and development especially flowering, ripening of fruits, apical hook development, and root and shoot growth. As well as it summarizes their interaction during various abiotic stress conditions.

• Keywords
• brassinosteroid, ethylene, plant growth, stress tolerance,
• MeSH
• Brassinosteroids metabolism   MeSH
• Ethylenes metabolism   MeSH
• Gene Expression Regulation, Plant MeSH
• Signal Transduction physiology   MeSH
• Plant Development physiology   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Brassinosteroids MeSH
• ethylene MeSH Browser
• Ethylenes MeSH

The volatile two-carbon hormone ethylene acts in concert with an array of signals to affect etiolated seedling development. From a chemical screen, we isolated a quinoline carboxamide designated ACCERBATIN (AEX) that exacerbates the 1-aminocyclopropane-1-carboxylic acid-induced triple response, typical for ethylene-treated seedlings in darkness. Phenotypic analyses revealed distinct AEX effects including inhibition of root hair development and shortening of the root meristem. Mutant analysis and reporter studies further suggested that AEX most probably acts in parallel to ethylene signaling. We demonstrated that AEX functions at the intersection of auxin metabolism and reactive oxygen species (ROS) homeostasis. AEX inhibited auxin efflux in BY-2 cells and promoted indole-3-acetic acid (IAA) oxidation in the shoot apical meristem and cotyledons of etiolated seedlings. Gene expression studies and superoxide/hydrogen peroxide staining further revealed that the disrupted auxin homeostasis was accompanied by oxidative stress. Interestingly, in light conditions, AEX exhibited properties reminiscent of the quinoline carboxylate-type auxin-like herbicides. We propose that AEX interferes with auxin transport from its major biosynthesis sites, either as a direct consequence of poor basipetal transport from the shoot meristematic region, or indirectly, through excessive IAA oxidation and ROS accumulation. Further investigation of AEX can provide new insights into the mechanisms connecting auxin and ROS homeostasis in plant development and provide useful tools to study auxin-type herbicides.

• Keywords
• Arabidopsis, auxin homeostasis, chemical genetics, ethylene signaling, herbicide, quinoline carboxamide, reactive oxygen species, triple response,
• MeSH
• Amino Acids, Cyclic metabolism   MeSH
• Arabidopsis genetics   metabolism   MeSH
• Quinolones metabolism   MeSH
• Ethylenes metabolism   MeSH
• Gene Expression MeSH
• Herbicides chemistry   MeSH
• Homeostasis MeSH
• Indoleacetic Acids metabolism   MeSH
• Arabidopsis Proteins metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Seedlings metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 1-aminocyclopropane-1-carboxylic acid MeSH Browser
• Amino Acids, Cyclic MeSH
• Quinolones MeSH
• ethylene MeSH Browser
• Ethylenes MeSH
• Herbicides MeSH
• Indoleacetic Acids MeSH
• Arabidopsis Proteins MeSH
• Reactive Oxygen Species MeSH

In plants, the multistep phosphorelay (MSP) pathway mediates a range of regulatory processes, including those activated by cytokinins. The cross talk between cytokinin response and light has been known for a long time. However, the molecular mechanism underlying the interaction between light and cytokinin signaling remains elusive. In the screen for upstream regulators we identified a LONG PALE HYPOCOTYL (LPH) gene whose activity is indispensable for spatiotemporally correct expression of CYTOKININ INDEPENDENT1 (CKI1), encoding the constitutively active sensor His kinase that activates MSP signaling. lph is a new allele of HEME OXYGENASE1 (HY1) that encodes the key protein in the biosynthesis of phytochromobilin, a cofactor of photoconvertible phytochromes. Our analysis confirmed the light-dependent regulation of the CKI1 expression pattern. We show that CKI1 expression is under the control of phytochrome A (phyA), functioning as a dual (both positive and negative) regulator of CKI1 expression, presumably via the phyA-regulated transcription factors (TF) PHYTOCHROME INTERACTING FACTOR3 and CIRCADIAN CLOCK ASSOCIATED1. Changes in CKI1 expression observed in lph/hy1-7 and phy mutants correlate with misregulation of MSP signaling, changed cytokinin sensitivity, and developmental aberrations that were previously shown to be associated with cytokinin and/or CKI1 action. Besides that, we demonstrate a novel role of phyA-dependent CKI1 expression in the hypocotyl elongation and hook development during skotomorphogenesis. Based on these results, we propose that the light-dependent regulation of CKI1 provides a plausible mechanistic link underlying the well-known interaction between light- and cytokinin-controlled plant development.

• MeSH
• Arabidopsis genetics   metabolism   radiation effects   MeSH
• Cytokinins metabolism   MeSH
• Phytochrome A genetics   metabolism   MeSH
• Plants, Genetically Modified MeSH
• Heme Oxygenase (Decyclizing) genetics   metabolism   MeSH
• Hypocotyl genetics   metabolism   radiation effects   MeSH
• Models, Genetic MeSH
• Mutation MeSH
• Protein Kinases genetics   metabolism   MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Gene Expression Regulation, Plant genetics   radiation effects   MeSH
• Signal Transduction genetics   radiation effects   MeSH
• Light * MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• CKI1 protein, Arabidopsis MeSH Browser
• Cytokinins MeSH
• Phytochrome A MeSH
• Heme Oxygenase (Decyclizing) MeSH
• HY1 protein, Arabidopsis MeSH Browser
• Protein Kinases MeSH
• Arabidopsis Proteins MeSH