The E3 ubiquitin ligase HOS1 is involved in ethylene regulation of leaf expansion inArabidopsis

Abstract

Ethylene regulates a variety of physiological processes, such as flowering, senescence, abscission, and fruit ripening. In particular, leaf expansion is also controlled by ethylene in Arabidopsis. Exogenous treatment with ethylene inhibits leaf expansion, and consistently, ethylene insensitive mutants show increased leaf area. Here, we report that the RING finger-containing E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1) regulates leaf expansion in an ethylene signaling pathway. The HOS1-deficient mutant showed reduced leaf area and was insensitive to ethylene perception inhibitor, silver thiosulfate (STS). Accordingly, genes encoding ethylene signaling components were significantly up-regulated in hos1-3. This study demonstrates that the HOS1 protein is involved in ethylene signal transduction for the proper regulation of leaf expansion possibly under environmentally stressful conditions.Leaf expansion is a crucial process that not only determines the shape and size of mature leaves but also ensures its photosynthetic capacity for plant growth and development. 1,2 It is influenced by multiplicity of environmental factors, such as water availability and day length. 3,4 In addition, endogenous hormone signaling is also intensively involved in the control of leaf expansion. Promotive roles of auxin, brassinosteroid, and gibberellin in leaf expansion have been demonstrated. [5][6][7] The simple hydrocarbon ethylene is a gaseous plant hormone that regulates a variety of developmental processes, such as seed germination, cell elongation, abscission, senescence, sex determination, and fruit ripening. [8][9][10][11][12][13] It has been also proposed that ethylene negatively regulates leaf expansion process. Exogenous ethylene treatment results in reduced leaf area. 14 Furthermore, ethylene insensitive mutants, such as ethylene receptor 1 (etr1) and ethylene response sensor 1 (ers1), show increased leaf size. 15,16 Five receptor isoforms are responsible for ethylene perception: ETR1, ETR2, ERS1, ERS2, and ETHYLENE INSENSITIVE 4 (EIN4). 17 Their ethylene perception is integrated into a negative regulator of ethylene signaling, CONSTITUTIVE TRIPLE RESPONSE 1 (CTR1) Ser/Thr protein kinase, 18 which in turn regulates a series of transcriptional cascades in order to control ethylene-dependent physiological processes. EIN2 is a representative positive signaling regulator and subsequently activates genes encoding EIN3 and related EIN3-LIKE (EIL), which further regulate expression of ETHYLENE-RESPONSE FACTORs (ERFs). 19,20 In the presence of ethylene, ethylene receptors inactivate kinase activity of CTR1 so that subsequent transcriptional cascades are activated. 21 Although ethylene signaling pathways have been intensively investigated, its intricate networks with other signaling pathways remain to be unraveled.The RING-type E3 ligase HOS1 was originally reported as cold signaling attenuator. 22 The cold-activated HOS1 protein executes protein turnover of the INDUCER OF CBF EXPRESSION1 (ICE1) MYC-l...

Phenotypic and genome‐wide association analysis of spike ethylene in diverse wheat genotypes under heat stress

“…8d). This SNP is predicted to be an E3-ubiquitin ligase (He et al, 2013), which is involved in the regulation of ET action by targeting ubiquitination of ACS proteins, particularly types 2 and 3 (Lee & Seo, 2015). Of the 873 E3-ligase genes identified so far in wheat, 173 genes are expressed differentially during grain development (Capron et al, 2012).…”

Characterization of the Key Region and Phosphorylation Sites of EcaICE1 for its Molecular Interaction with EcaHOS1 Protein from Eucalyptus camaldulensis

“…E3-ubiquitin-ligases-mediated ubiquitination are emerging as major regulators in plants’ response to abiotic stress, circadian rhythm control, cell cycling and plant-microbe interactions [29,30,31]. High expression of osmotically responsive genes1 (HOS1), one of the RING finger-containing E3 ubiquitin ligase, was initially described as a cold-signaling attenuator of ICE1 [9,32], and also involved in ethylene signal transduction [33] and photoperiodic flowering [34] in Arabidopsis . It is reported that most of the plant species just have a single copy of the HOS1 gene [35], suggesting that HOS1 would have important roles in various plant species.…”

Rice root curling, a response to mechanosensing, is modulated by the rice E3-ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 (OsHOS1)

“…Recently, it has been suggested that HOS1 is also involved in ethylene and auxins responses. 18,19 Therefore, a cross-talk between the HOS1 associated processes and different plant hormones is expected.…”