Effect of RNAi-mediated silencing of the TaAOS2 gene on phytohormone accumulation, growth and productivity in bread wheat.

Abstract

Reverse genetics methods are actively used in plant biology to study the functions of specific genes responsible for the adaptation of plants to various environmental stresses. The present study describes the production and primary characterization of transgenic bread wheat with silenced expression of allen oxide synthase (AOS). AOS is a key enzyme involved in the initial step of biosynthesis of stress-related phytohormones known as jasmonates. To induce silencing of AOS in wheat, we designed the RNA interference (RNAi) vector containing an inverted repeat region of the TaAOS2 gene cloned from genome DNA of cv. Chinese Spring. With the help of biolistic-mediated transformation, a number of transgenic Chinese Spring plants have been produced. Real-Time PCR analysis confirmed the suppression of target gene expression, since transgenic dsRNAi lines accumulated only 21-44 % mRNA of TaAOS2 after leaf wounding compared to the wound-induced level in non-transgenic control. Gas chromatography-mass spectrometry revealed that the silencing of TaAOS2 substantially reduced the accumulation of jasmonic acid (JA) and jasmonoyl-isoleucine conjugate (JA-Ile), while the production of other phytohormones, such as abscisic acid and salicylic acid, was not affected. TaAOS2-silenced lines were characterized by shorter leaves at the juvenile stage, demonstrated a tendency towards reduced plant height and decreased grain weight, while the average flowering time and plant fertility (number of seeds per spike) were not affected. The obtained transgenic lines in combination with AOS-overexpressing lines can be used for further detailed analysis of the adaptive responses controlled by the jasmonate hormonal system.