Infection-induced rapid cell death in plants: a means of efficient pathogen defense

Abstract

The hypersensitive reaction represents one of the major means by which plants actively defend themselves against infection by pathogenic bacteria, fungi, viruses, and nematodes. This complex defense reaction, often associated with the synthesis of phytoalexins (antimicrobial secondary metabolites), involves at the cellular level highly dynamic cytoplasmic rearrangements, rapid metabolic changes, and finally cell death. It also correlates with the rapid and transient activation of various defense-related genes in a region of tissue surrounding infection sites and later, with the systemic increase in expression of a number of other genes. Examination of the reactions of individual living cells of potato leaves infected with Phytophthora infestans enabled the comprehensive description of the dynamic aspects of all stages of the defense response. Cytochemical investigations, employing cultured cells of parsley infected with P. infestans as a versatile model system, have contributed to a better understanding of cytoplasmic and metabolic processes occurring during the defense response, and suggest that hypersensitive cell death requires the preceding activation of respiration and specific metabolic pathways. Key words: defense responses, defense-related genes, hypersensitive reaction, programmed cell death.

Resistance of Nicotiana benthamiana to Phytophthora infestans Is Mediated by the Recognition of the Elicitor Protein INF1

“…As previously observed in other resistance interactions between plants and P. infestans (Gross et al, 1993;Schmelzer et al, 1995;Naton et al, 1996;V.G.A.A. Vleeshouwers, F. Govers, and L. Colon, unpublished results), penetration of an epidermal cell by a germinating cyst of P. infestans was noted in all combinations that were examined.…”

“…Later, infected tissue necrotizes, and the mycelium develops sporangiophores that emerge through the stomata to produce numerous asexual spores called sporangia. Penetration of an epidermal cell by P. infestans has been noted in all examined interactions, including those with plant species unrelated to the solanaceous hosts (Gross et al, 1993;Schmelzer et al, 1995;Naton et al, 1996; V.G.A.A. Vleeshouwers, F. Govers, and L. Colon, unpublished data).…”

“…This was demonstrated directly by infiltration of Avr proteins into plant leaves or indirectly by expression of Avr genes in plant cells containing the corresponding R gene (Culver and Dawson, 1991;de Wit, 1995;Alfano and Collmer, 1996;Knogge, 1996;Bonas and van den Ackerveken, 1997;van den Ackerveken and Bonas, 1997). Elicitor treatment or Avr gene expression triggers the HR and related defense responses in plants that mimic the response induced by avirulent pathogens (Hahlbrock et al, 1995;Hammond-Kosack and Jones, 1996). R genes, on the other hand, are thought to encode specific receptors that interact directly or indirectly with elicitors, thereby initiating signal transduction pathways that lead to the HR and expression of disease resistance response (Staskawicz et al, 1995;Bent, 1996;Hammond-Kosack andJones, 1996, 1997;Baker et al, 1997).…”

“…Vleeshouwers, F. Govers, and L. Colon, unpublished data). Fully resistant plants, such as some of the potato lines bearing R genes or the nonhosts Solanum nigrum and parsley, display a typical localized HR at all infection sites (Gees and Hohl, 1988; Colon et al, 1992; Gross et al, 1993; Freytag et al, 1994;Schmelzer et al, 1995;Naton et al, 1996), suggesting that the classic model of pathogen elicitor recognition by a plant receptor and the subsequent activation of signal transduction pathways leading to HR could mediate these interactions.P. infestans is generally considered a specialized pathogen.…”

Correlation of Rapid Cell Death with Metabolic Changes in Fungus-Infected, Cultured Parsley Cells

“…glycínea (Jahnen and Hahlbrock, 1988;Schmelzer et al, 1989) and exhibited major features of the early plant defense reactions that we observed in the potato cells. It proved to be very useful in investigating the participation of the cytoskeleton in the translocation of cytoplasm and nucleus as well as the simultaneous expression of defense-related genes (Gross et al, 1993;Schmelzer et al, 1995).…”