Plant defense genes are regulated by ethylene

Abstract

One of the earliest detectable events during plant-pathogen interaction is a rapid increase in ethylene biosynthesis. This gaseous plant stress hormone may be a signal for plants to activate defense mechanisms against invading pathogens such as bacteria, fungi, and viruses. The effect of ethylene on four plant genes involved in three separate plant defense response pathways was examined; these included (i and ii) genes that encode L-phenylalanine ammonia-lyase (EC 4.3.1.5) and 4-coumarate:CoA ligase [4-coumarate:CoA ligase (AMP-forming), EC 6.2.1.12], enzymes of the phenylpropanoid pathway, (iii) the gene encoding chalcone synthase, an enzyme of the flavonoid glycoside pathway, and (iv) the genes encoding hydroxyproline-rich glycoprotein, a major protein component(s) of plant cell walls. Blot hybridization analysis of mRNA from ethylene-treated carrot roots reveals marked increases in the levels of phenylalanine ammonia-lyase mRNA, 4-coumarate CoA ligase mRNA, chalcone synthase mRNA, and certain hydroxyproline-rich glycoprotein transcripts. The effect of ethylene on hydroxyproline-rich glycoprotein mRNA accumulation was different from that of wounding. Ethylene induces two hydroxyproline-rich glycoprotein mRNAs (1.8 and 4.0 kilobases), whereas wounding of carrot root leads to accumulation of an additional hydroxyproline-rich mRNA (1.5 kilobases). These results indicate that at least two distinct signals, ethylene and a wound signal, can affect the expression of plant defense-response genes.

Ethylene Modulates Flavonoid Accumulation and Gravitropic Responses in Roots of Arabidopsis

“…These sustained flavonoid increases were completely absent in the etr1-3 and ein2-5 mutants, consistent with ETR1-and EIN2-dependent mechanisms controlling this flavonoid accumulation pattern. Consistent with this result, CHS gene expression is induced in a number of species by environmental factors (Winkel-Shirley, 2002), including ethylene (Ecker and Davis, 1987;Ryder et al, 1987;Schmid et al, 1990;McKhann and Hirsch, 1994). Furthermore, ACC treatment blocks the transient flavonoid accumulation in the root tip that occurs about 2 h after gravitropic stimulation (Buer and Muday, Figure 6.…”

Calcium Requirement for Ethylene-Dependent Responses.

“…One pathway is ethylene dependent and is exemplified by ethylene itself (Boller et al, 1983;Ecker and Davis, 1987). It also includes elicitors, such as a-aminobutyric acid (a-AB), that promote ethylene production and require ethylene in their mode of action (Lotan and Fluhr, 1990b;Eyal and Fluhr, 1992).…”

“…Ethylene biosynthesis is rapidly increased during plant-pathogen interaction or application of chemical elicitors (Yang, 1985;Lotan and Fluhr, 199Oa). Ethylene subsequently induces a multitude of gene arrays collectively called the pathogenesis response (Van Loon and Antoniw, 1982;Ecker and Davis, 1987;Eyal and Fluhr, 1992). Pathogenesis-related (PR) proteins are encoded by gene families that are coordinately expressed as part of this response and are examples of the nonspecific host reaction to pathogen invasion (Meins and Ahl, 1989;BOI et al, 1990).…”

Hormonal and Stress Induction of the Gene Encoding Common Bean Acetyl-Coenzyme A Carboxylase

“…In addition to oxylipins, ethylene has also been implicated in the activation of systemic plant defenses in response to pathogens (Penninckx et al, 1998) and wounding (O'Donnell et al, 1996). In Arabidopsis, ethylene also provokes an increase in flavonoid accumulation (Buer et al, 2006) and in carrot (Daucus carota) induces genes for flavonoid synthesis (Ecker and Davis, 1987). The JA and ethylene signaling pathways are induced concomitantly in Arabidopsis to activate defense responses after infection with a necrotrophic pathogen (Penninckx et al, 1998), but, after wounding, an antagonistic interaction between JA and ethylene was proposed for the local responses in Arabidopsis leaves (Rojo et al, 1999).…”