Planta

, Volume 165, Issue 3, pp 311–321

Tagetitoxin affects plastid development in seedling leaves of wheat

  • J. H. Lukens
  • R. D. Durbin
Article

DOI: 10.1007/BF00392227

Cite this article as:
Lukens, J.H. & Durbin, R.D. Planta (1985) 165: 311. doi:10.1007/BF00392227

Abstract

Ultrastructural and biochemical approaches were used to investigate the mode of action of tagetitoxin, a nonhost-specific phytotoxin produced by Pseudomonas syringae pv. tagetis (Hellmers) Young, Dye and Wilkie, which causes chlorosis in developing — but not mature — leaves. Tagetitoxin has no effect on the growth rate or morphology of developing leaves of wheat (Triticum aestivum L.) seedlings. Its cytological effects are limited to plastid aberrations; in both light-and dark-grown leaves treated with toxin, internal plastid membranes fail to develop normally and plastid ribosomes are absent, whereas mitochondrial and cytoplasmic ribosomes are unaffected. The activity of a plastid stromal enzyme, ribulose-1,5-bisphosphate carboxylase (RuBPCase, EC 4.1.1.39), which is co-coded by nuclear and chloroplast genes, is markedly lower in extracts of both light-and dark-grown toxin-treated leaves, whereas the activity of another stromal enzyme, NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-G-3P-DH, EC 1.2.1.13), which is coded only by the nuclear genome, is significantly lower in extracts of light-grown, but not of dark-grown, treated leaves. The mitochondrial enzymes fumarase (EC 4.2.1.2) and cytochrome-c oxidase (EC 1.9.3.1) are unaffected by toxin in dark-grown leaves, but fumarase activity is reduced in light-grown ones. Four peroxisomal enzyme activities are lowered by toxin treatment in both light- and dark-grown leaves. Light- and dark-grown, toxintreated leaves contain about 50% and 75%, respectively, of the total protein of untreated leaves. There are threefold and twofold increases in free amino acids in light-grown and dark-grown treated leaves, respectively. In general, the effects of tagetitoxin are more extensive and exaggerated in light-grown than in dark-grown leaves. We conclude that tagetitoxin interferes primarily with a light-independent aspect of chloroplast-specific metabolism which is important in plastid biogenesis.

Key words

Chloroplast developmentChloroplast ribosomesEtioplast (prolamellar body)Pseudomonas (toxin)TagetitoxinTriticum (chloroplast development)

Abbreviations

NADP-G-3-DH

NADP-glyceraldehyde-3-phosphate dehydrogenase

PLB

prolamellar body

RuBP-Case

ribulose-1,5-bisphosphate carboxylase

SADH

shikimic acid dehydrogenase

Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • J. H. Lukens
    • 1
    • 2
    • 3
  • R. D. Durbin
    • 1
    • 2
  1. 1.Department of Plant PathologyUniversity of WisconsinMadisonUSA
  2. 2.Agricultural Research ServiceU.S. Department of AgricultureMadisonUSA
  3. 3.Biological LaboratoriesHarvard UniversityCambridgeUSA