Rhizobitoxine-induced chlorosis occurs in coincidence with methionine deficiency in soybeans.

Abstract

BACKGROUND AND AIMS:

Rhizobitoxine, produced by the legume symbiont Bradyrhizobium elkanii, inhibits cystathionine-beta-lyase (EC 4.4.1.8) in methionine biosynthesis and 1-aminocyclopropane-1-carboxylate synthase (ACC) in ethylene biosynthesis. Rhizobitoxine production by B. elkanii enhances nodulation of host legumes via the inhibition of ethylene synthesis, but causes foliar chlorosis in susceptible soybeans, though how it does so remains to be investigated. The aim of this study was to examine the physiological basis of rhizobitoxine-induced chlorosis in soybeans.

METHODS:

Wild-type B. elkanii and a rhizobitoxine-deficient mutant were inoculated in Glycine max 'Lee'. Thirty days after inoculation, the upper parts of soybean shoots were analysed for amino acid contents. Chlorotic soybeans inoculated with wild-type B. elkanii were treated with methionine and ACC to assess the effects of the chemicals on the chlorosis.

KEY RESULTS:

Chlorotic upper shoots of soybeans inoculated with wild-type B. elkanii had a lower methionine content and higher accumulation of the methionine precursors than those with the rhizobitoxine-deficient mutant. In addition, the foliar chlorosis was alleviated by the application of methionine.

CONCLUSIONS:

Rhizobitoxine-induced chlorosis occurs in coincidence with methionine deficiency as a result of cystathione-beta-lyase inhibition during methionine biosynthesis.

• Authors: Shin Okazaki, Masayuki Sugawara, Ken-ichi Yuhashi, Kiwamu Minamisawa
• Journal: Annals of botany (Ann Bot) Vol. 100 Issue 1 Pg. 55-9 (Jul 2007) ISSN: 0305-7364 [Print] England
• PMID: 17525098 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Plant Proteins
• Propanolamines
• Methionine
• Lyases
• cystathionine beta-lyase
• rhizobitoxine

Topics

• Immunity, Innate (genetics, physiology)
• Lyases (genetics, metabolism)
• Methionine (metabolism)
• Plant Diseases (chemically induced)
• Plant Leaves (drug effects, metabolism)
• Plant Proteins (genetics, metabolism)
• Plant Shoots (drug effects, metabolism)
• Propanolamines (pharmacology)
• Soybeans (drug effects, genetics, metabolism)