ABSTRACT
Plant development depends on the perception of external cues, such as light, gravity, touch, wind or nutrients, among others. Nevertheless, little is known regarding signal transduction pathways integrating these stimuli. Recently, we have reported the involvement of a rice E3-ubiquitin ligase (OsHOS1, HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1), previously associated with abiotic stress response, in root responses to mechanical stimuli. We showed that OsHOS1 is involved in the regulation of root curling after mechanosensing and that RNAi::OsHOS1 plants failed to exhibit the root curling phenotype observed in WT. Interestingly, the straight root phenotype of these transgenics correlated with the up-regulation of rice ROOT MEANDER CURLING (OsRMC, a negative regulator of rice root curling) and was reverted by the exogenous application of jasmonic acid. Altogether, our results highlight the role of the proteasome modulating plant responses to mechanical stimuli and suggest that OsHOS1 is a hub integrating environmental and hormonal signaling into plant growth and development.
Subject(s)
Oryza/metabolism , Plant Roots/metabolism , Cyclopentanes/pharmacology , Gene Expression Regulation, Plant/drug effects , Mechanotransduction, Cellular/drug effects , Oryza/drug effects , Oryza/enzymology , Oxylipins/pharmacology , Plant Proteins/genetics , Plant Proteins/metabolism , Plant Roots/drug effects , Plant Roots/enzymology , Plants, Genetically Modified/drug effects , Plants, Genetically Modified/enzymology , Plants, Genetically Modified/metabolism , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolismABSTRACT
1-Aminocyclopropane-1-carboxylate (ACC) synthase (ACS; EC 4.4.1.14) is the key regulatory enzyme of the ethylene biosynthetic pathway and is encoded by a multigene family in Arabidopsis thaliana, tomato, mung bean and other plants. Southern blot analysis revealed the existence of at least five ACS genes in white lupin (Lupinus albus L.) genome. Four complete and one partial sequences representing different ACS genes were cloned from the lupin genomic library. The levels of expression of two of the genes, LA-ACS1 and LA-ACS3, were found to increase after hypocotyl wounding. Apparently, these two genes were up-regulated by exogenous IAA treatment of seedlings. The LA-ACS3 mRNA levels were also elevated in the apical part of hypocotyl, which is reported to contain a high endogenous auxin concentration. This gene may be involved in the auxin- and ethylene-controlled apical hook formation. The expression of the LA-ACS4 gene was found to be almost undetectable. This gene may represent a "silent" twin of LA-ACS5 as these two genes share a considerable level of homology in coding and non-coding regions. The LA-ACS5 mRNA is strongly up-regulated in the embryonic axis of germinating seeds at the time of radicle emergence, and was also found in roots and hypocotyls of lupin seedlings.
