No.42 - è¾²æ¥­ç”Ÿç‰©è³‡æºç ”ç©¶æ‰€

Gamma Field Symposia, No. 42, 2003 Institute of Radiation Breeding
NIAS, Japan
ETHYLENE-SIGNALING PATHWAY
41
MOLECULAR MECHANISMS FOR ETHYLENE PERCEPTION
AND SIGNAL TRANSDUCTION
Takashi HIRAYAMA 1), 2) and Tsutomu UGAJIN 2)
1)
Laboratory of Plant Molecular Biology, Yokohama Institute, RIKEN
2)
Graduate School of Integrated Science, Yokohama City Univ.
1-7-29, Suehiro, Tsurumi, Yokohama, Kanagawa, 230-0045, Japan
Introduction
The gaseous plant hormone ethylene is involved in a variety of growth and developmental
processes including germination, cell elongation, flower and leaf senescence, sex determination
and fruit ripening. To gain insight into the molecular mechanisms of ethylene action, a molecular
genetic approach has been applied using the ethylene-evoked triple response phenotype of
Arabidopsis seedlings. Analysis of those ethylene related mutants allowed us to draw the overall
structure of the ethylene signal transduction pathway, from ethylene perception to nuclear events.
Based on the similarity of the sensor proteins, the ethylene signal transduction pathway has been
thought to be similar to the yeast osmosensing signaling pathway. However, recent studies have
revealed that the ethylene pathway is unique and quite complicated. Although the ethylenesignaling
pathway is most understood among the signal transduction pathways for plant hormones,
there are still many matters to be clarified. Here, we are going to describe the recent studies on the
ethylene-signaling components and discuss the possible model for the ethylene-signaling pathway.
Isolation of ethylene related mutants
A gaseous hormone ethylene is involved in diverse developmental and physiological
processes of plants. Treatment of etiolated seedlings with ethylene evokes dramatic morphological
changes referred to as the “triple response” that includes exaggerated apical hook, radial swelling
of hypocotyl and inhibition of hypocotyl and root elongation in Arabidopsis. These morphological
changes are highly specific for ethylene. A genetic approach that relies on the triple response
phenotype as a morphological marker has allowed the identification of several classes of mutants
with impaired responses to ethylene (BLEECKER et al. 1988; GUZMAN and ECKER 1990). These
mutants can be classified into several groups; ethylene insensitive mutant, etr1, etr2, ein2, ein3,
ein4, ein5/ain1 and ein6; constitutive ethylene response mutant, eto1, 2, 3 and ctr1; and tissue-