Journal Article

Salicylic acid inhibits gibberellin-induced alpha-amylase expression and seed germination via a pathway involving an abscisic-acid-inducible WRKY gene

Zhang, Zhong-Lin, Hanzlik, Shane, Xie, Zhen, Cook, Everett, Shen, Qingxi J

2007

Overview

It is well known that abscisic acid (ABA) antagonizes gibberellin (GA)-promoted seed germination. Recent circumstantial evidence suggests that salicylic acid (SA) also inhibits seed germination in maize and Arabidopsis. Our study shows that SA blocks barley seed germination in a dosage dependent manner. As an initial effort to addressing the mechanism controlling the crosstalk of SA, GA and ABA signaling in barley, we studied the regulation of α-amylases by SA and a WRKY gene whose expression is modulated by these hormones. Assays of α-amylase activity reveal that GA-induced α-amylase production in aleurone cells is inhibited by bioactive SA, but not its analogs, 3-hydroxybenzoic acid and 4-hydroxybenzoic acid. This inhibitory effect is unlikely due to repressing α-amylase secretion or inhibiting α-amylase enzyme activities. Northern blot analyses indicate that SA suppresses GA-induced expression of a barley low pI α-amylase gene (Amy32b). Because our previous data indicate that ABA-inducible and GA-suppressible WRKY genes inhibit the expression of α-amylase genes in rice, we studied the steady state mRNA levels of a barley WRKY gene, HvWRKY38. The expression of HvWRKY38 in barley aleurone cells is down-regulated by GA, but up-regulated by SA and ABA. However, the regulation of HvWRKY38 by SA appears to be different from that of ABA in term of the kinetics and levels of induction. Over-expression of HvWRKY38 in aleurone cells by particle bombardment blocks GA induction of the Amy32b promoter reporter construct (Amy32b-GUS). Therefore, HvWRKY38 might serve as a converging node of SA and ABA signal pathways involved in suppressing GA-induced seed germination.

• Publisher: Dordrecht : Kluwer Academic Publishers,Springer Nature B.V
• Subject: 4-hydroxybenzoic acid / Abscisic acid / aleurone cells / alpha-amylase / alpha-Amylases / alpha-Amylases - biosynthesis / alpha-Amylases - genetics / antagonists & inhibitors / Arabidopsis / Barley / biosynthesis / corn / drug effects / embryology / Enzymatic activity / enzyme activity / enzymology / Gene Expression Regulation, Plant / Gene Expression Regulation, Plant - drug effects / Genes / genetics / Germination / Germination - drug effects / gibberellic acid / Gibberellins / Gibberellins - antagonists & inhibitors / Gibberellins - pharmacology / growth & development / Hordeum / Hordeum - embryology / Hordeum - enzymology / Hordeum - genetics / Hordeum vulgare / Hormones / messenger RNA / metabolism / mRNA / Northern blotting / Oryza sativa / Overexpression / p-Hydroxybenzoic acid / Particle bombardment / pharmacology / Plant Proteins / Plant Proteins - biosynthesis / Plant Proteins - genetics / Plant Proteins - metabolism / Repressor Proteins / Repressor Proteins - biosynthesis / Repressor Proteins - genetics / Repressor Proteins - metabolism / rice / Salicylic acid / Salicylic Acid - pharmacology / secretion / Seed germination / Seeds / Seeds - growth & development / Signal Transduction / Signaling / WRKY / Zea mays / α-Amylase