Effects of Jasmonic Acid on Embryo-Specific Processes in Brassica and Linum Oilseeds

Abstract

A number of effects on embryogenesis of the putative phytohormone jasmonic acid (JA), and its methyl ester (MeJA), were investigated in two oilseed plants, rapeseed (Brassica napus) and flax (Linum usitatissimum). Results from treatments with JA and MeJA were compared with those of a known effector of several aspects of embryogenesis, abscisic acid (ABA). Jasmonic acid was identified by gas chromatography-mass spectrometry as a naturally occurring substance in both plant species during embryo development. Both JA and MeJA can prevent precocious germination of B. napus microspore embryos and of cultured zygotic embryos of both species at an exogenous concentration of >1 micromolar. This dose-response was comparable with results obtained with ABA. Inhibitory effects were also observed on seed germination with all three growth regulators in rapeseed and flax. A number of molecular aspects of embryogenesis were also investigated. Expression of the B. napus storage protein genes (napin and cruciferin) was induced in both microspore embryos and zygotic embryos by the addition of 10 micromolar JA. The level of napin and cruciferin mRNA detected was similar to that observed when 10 micromolar ABA was applied to these embryos. For MeJA only slight increases in napin or cruciferin mRNA were observed at concentrations of 30 micromolar. Several oilbody-associated proteins were found to accumulate when the embryos were incubated with either JA or ABA in both species. The MeJA had little effect on oilbody protein synthesis. The implications of JA acting as a natural regulator of gene expression in zygotic embryogenesis are discussed.

The Tomato Homolog of CORONATINE-INSENSITIVE1 Is Required for the Maternal Control of Seed Maturation, Jasmonate-Signaled Defense Responses, and Glandular Trichome Development[W]

“…Because cell division and expansion in fruit tissues is dependent on normal embryo and seed development (Gillaspy et al, 1993;Giovannoni, 2001), this hypothesis would explain the reduced size of jai1 fruit. A role for LeCOI1 in embryogenesis also is consistent with the abundance of JAs in tomato ovaries (Hause et al, 2000) as well as with previous studies implicating JA as an endogenous regulator of embryo development in oilseeds (Wilen et al, 1991;Hays et al, 1999). Whether endogenous JAs regulate reproductive function in tomato remains to be established.…”

“…Correlations between endogenous JA levels in specific tissues and the effects of the applied hormone have provided evidence that JAs have a role in promoting senescence, fruit ripening, embryo development, and the accumulation of storage proteins (Staswick, 1990;Wilen et al, 1991;Creelman and Mullet, 1997;He et al, 2002). However, because exogenous JAs do not target specific cell types and often are administered at nonphysiological concentrations, confirmation of these roles requires genetic manipulation of either endogenous JA levels or the signal transduction steps that couple JA production to the physiological response.…”

A Wound- and Methyl Jasmonate-Inducible Transcript Coding for a Myrosinase-Associated Protein with Similarities to an Early Nodulin

“…Possibly some of the MyAP (or related) transcripts in the healthy plant are regulated by endogenous jasmonates. However, to our knowledge the only data concerning endogenous jasmonates in B. napus is from seed (Wilen et al, 1990). In addition, it is not always the case that high amounts endogenous jasmonates correspond to high levels of jasmonate-inducible transcripts (Creelman and Mullet, 1995).…”

12-Oxo-Phytodienoic Acid Accumulation during Seed Development Represses Seed Germination inArabidopsis

“…It has been reported that JA/MeJA is capable of inhibiting seed germination in Brassica napus, Linum usitatissimum, Solanum lycopersicum, and Arabidopsis (Wilen et al, 1991; (B) to (D) ABA (B), GA 4 (C), and GA 1 (D) levels in cts-2 and Ws dry seeds and over a time course of 2 d during which stratified seeds were placed under germination conditions. (E) Germination frequency of cts-2 and Ws stratified seeds.…”