Effect of Salt Stress on Germin Gene Expression in Barley Roots

Germin gene expression in barley (Hordeum vulgare L.) seedlings responds to developmental and environmental cues. During seed germination, germin mRNA levels were maximal 2 d after the start of imbibition in control seedlings and declined to low levels by 6 d. When seeds were sown in the presence of 200 mM NaCl, germin mRNA levels were also maximal after 2 d, but NaCl treatment, which slowed seedling growth, prolonged 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 transition region than in shoots. In roots of 6-d-old seedlings, germin gene expression was regulated by salt shock and plant growth regulators. Induced germin mRNA levels were maximal 8 h after treatment with NaCl, salicylate, methyl salicylate, or methyl jasmonate and 4 h after treatment with abscisic acid and indoleacetic acid. Like germin mRNA, dehydrin mRNA levels were maximal 8 h after NaCl treatment. In contrast, peroxidase mRNA levels declined to less than control levels within 30 min of treatment. Germin gene expression is regulated developmentally by salt stress and by treatments with plant hormones. Since germin is an oxalate oxidase, these result imply that oxalate has important roles in plant development and homeostasis.