An Endoplasmic Reticulum-Derived Structure That Is Induced under Stress Conditions in Arabidopsis

Abstract

The endoplasmic reticulum (ER) body is a characteristic structure derived from ER and is referred to as a proteinase-sorting system that assists the plant cell under various stress conditions. Fluorescent ER bodies were observed in transgenic plants of Arabidopsis expressing green fluorescent protein fused with an ER retention signal. ER bodies were widely distributed in the epidermal cells of whole seedlings. In contrast, rosette leaves had no ER bodies. We found that wound stress induced the formation of many ER bodies in rosette leaves. ER bodies were also induced by treatment with methyl jasmonate (MeJA), a plant hormone involved in the defense against wounding and chewing by insects. The induction of ER bodies was suppressed by ethylene. An electron microscopic analysis showed that typical ER bodies were induced in the non-transgenic rosette leaves treated with MeJA. An experiment using coi1 and etr1-4 mutant plants showed that the induction of ER bodies was strictly coupled with the signal transduction of MeJA and ethylene. These results suggested that the formation of ER bodies is a novel and unique type of endomembrane system in the response of plant cells to environmental stresses. It is possible that the biological function of ER bodies is related to defense systems in higher plants.

NAI1 Gene Encodes a Basic-Helix-Loop-Helix–Type Putative Transcription Factor That Regulates the Formation of an Endoplasmic Reticulum–Derived Structure, the ER Body

“…MeJA induces the formation of ER body-like structures (i-ER bodies) in rosette leaves that have no ER bodies under normal conditions (Matsushima et al, 2002). The shapes and sizes of ER bodies and i-ER bodies are so similar that the molecular mechanism(s) underlying the formation of these structures may be shared.…”

“…A large number of ER bodies are observed in cotyledons, hypocotyls, and roots of young seedlings (Matsushima et al, 2002). Cotyledons decrease the number of ER bodies during senescence, whereas hypocotyls and roots maintain the ER bodies (Matsushima et al, 2002). In contrast with seedlings, rosette leaves of mature plants have few ER bodies and have GFP fluorescence only in ER networks (Matsushima et al, 2002).…”

“…Cotyledons decrease the number of ER bodies during senescence, whereas hypocotyls and roots maintain the ER bodies (Matsushima et al, 2002). In contrast with seedlings, rosette leaves of mature plants have few ER bodies and have GFP fluorescence only in ER networks (Matsushima et al, 2002). However, many spindle-shaped structures can be induced in rosette leaves by wounding them or treating them with exogenous methyl jasmonate (MeJA), a plant hormone that induces a defense response against wounding and chewing by insects (Matsushima et al, 2002).…”

“…A large number of ER bodies are observed in cotyledons, hypocotyls, and roots of young seedlings (Matsushima et al, 2002). Cotyledons decrease the number of ER bodies during senescence, whereas hypocotyls and roots maintain the ER bodies (Matsushima et al, 2002).…”

“…In contrast with seedlings, rosette leaves of mature plants have few ER bodies and have GFP fluorescence only in ER networks (Matsushima et al, 2002). However, many spindle-shaped structures can be induced in rosette leaves by wounding them or treating them with exogenous methyl jasmonate (MeJA), a plant hormone that induces a defense response against wounding and chewing by insects (Matsushima et al, 2002). The induced structures have shapes and sizes similar to those of ER bodies of seedlings.…”