The rice RING finger E3 ligase, OsHCI1, drives nuclear export of multiple substrate proteins and its heterogeneous overexpression enhances acquired thermotolerance

Abstract

Thermotolerance is very important for plant survival when plants are subjected to lethally high temperature. However, thus far little is known about the functions of RING E3 ligase in response to heat shock in plants. This study found that one rice gene encoding the RING finger protein was specifically induced by heat and cold stress treatments but not by salinity or dehydration and named it OsHCI1 (Oryza sativa heat and cold induced 1). Subcellular localization results showed that OsHCI1 was mainly associated with the Golgi apparatus and moved rapidly and extensively along the cytoskeleton. In contrast, OsHCI1 may have accumulated in the nucleus under high temperatures. OsHCI1 physically interacted with nuclear substrate proteins including a basic helix-loop-helix transcription factor. Transient co-overexpression of OsHCI1 and each of three nuclear proteins showed that their fluorescent signals moved into the cytoplasm as punctuate formations. Heterogeneous overexpression of OsHCI1 in Arabidopsis highly increased survival rate through acquired thermotolerance. It is proposed that OsHCI1 mediates nuclear–cytoplasmic trafficking of nuclear substrate proteins via monoubiquitination and drives an inactivation device for the nuclear proteins under heat shock.

The RING Finger Ubiquitin E3 Ligase OsHTAS Enhances Heat Tolerance by Promoting H2O2-Induced Stomatal Closure in Rice

“…In addition to the two canonical RING types, additional types of modified RING domains, named RING-V, RING-D, RING-S/T, RING-G, and RING-C2, have been identified in Arabidopsis (Arabidopsis thaliana; Kosarev et al, 2002;Stone et al, 2005). Proteins harboring a RING domain are believed to play a role as ubiquitin ligases (E3) for the recognition and ubiquitylation of substrate proteins (Stone et al, 2005;Lim et al, 2013a). A number of RING E3s have been reported to play crucial roles in the posttranslational regulation of plant hormone signaling pathways, such as ABA and environmental stresses (Lim et al, 2013b).…”

“…The C3HC4 RING finger E3 ligase OsDIS1, which is predominantly localized in the nucleus, plays a negative role in drought stress tolerance through the transcriptional regulation of diverse stress-related genes and possibly through the posttranslational regulation of OsNek6 in rice (Ning et al, 2011). The rice RING finger E3 ligase HEAT AND COLD INDUCED1 drives the nuclear export of multiple substrate proteins, and its heterogenous overexpression enhances acquired thermotolerance (Lim et al, 2013a). A novel membranebound RING-V (C4HC3) protein from Brassica napus, BnTR1, is likely to be involved in mediating Ca 2+ dynamics by regulating the activity of calcium channels, which further alters the transcription of heat shock factors and heat shock proteins contributing to plant thermotolerance (Liu et al, 2014).…”

Ubiquitination pathway as a target to develop abiotic stress tolerance in rice

“…5 All of these studies confirm the possibility of developing thermal tolerance in plants through the ubiquitination pathway.…”

“…5,33 Plants are capable of acclimating to survive at extreme temperatures, a process which involves cell membrane protection, solute synthesis and accumulation, and specific enzymatic activities. 7,34 Not all mechanisms involved in the acclimation process are known.…”

“…2 The oscillations observed in annual production of this culture derive mainly from abiotic stresses, such as high salinity, drought, extreme temperatures, and chemical toxicity, which limit plant germination, development, and productivity. [3][4][5] It is estimated that environmental stresses can result in losses of up to 60% in grain productivity and, frequently, restrict the area in which the plant is cultivated. 6 Several studies focused on the key mechanisms of environmental stresses responses that can be used in genetic engineering in order to develop tolerant plants.…”