EFFECT OF SALT STRESS ON GERMIN GENE-EXPRESSION IN BARLEY ROOTS

Germin gene expression in barley (Hordeum vulgare L.) seedlings respon ds to developmental and environmental cues. During seed germination, g ermin mRNA levels were maximal 2 d after the start of imbibition in co ntrol seedlings and declined to low levels by 6 d. When seeds were sow n in the presence of 200 mM NaCl, germin mRNA levels were also maximal after 2 d, but NaCl treatment, which slowed seedling growth, prolonge d germin gene expression for an additional 1 d. In 4-d-old seedlings, germin mRNA levels were highest in roots and higher in the vascular tr ansition region than in shoots. In roots of 6-d-old seedlings, germin gene expression was regulated by salt shock and plant growth regulator s. Induced germin mRNA levels were maximal 8 h after treatment with Na Cl, salicylate, methyl salicylate, or methyl jasmonate and 4 h after t reatment with abscisic acid and indoleacetic acid. Like germin mRNA, d ehydrin mRNA levels were maximal 8 h after NaCl treatment. In contrast , peroxidase mRNA levels declined to less than control levels within 3 0 min of treatment. Germin gene expression is regulated developmentall y by salt stress and by treatments with plant hormones. Since germin i s an oxalate oxidase, these results imply that oxalate has important r oles in plant development and homeostasis.