RNAi of the sesquiterpene cyclase gene for phytoalexin production impairs pre- and post-invasive resistance to potato blight pathogens.

Potato antimicrobial sesquiterpenoid phytoalexins lubimin and rishitin have been implicated in resistance to the late blight pathogen, Phytophthora infestans and early blight pathogen, Alternaria solani. We generated transgenic potato plants in which sesquiterpene cyclase, a key enzyme for production of lubimin and rishitin, is compromised by RNAi to investigate the role of phytoalexins in potato defence. The transgenic tubers were deficient in phytoalexins and exhibited reduced post-invasive resistance to an avirulent isolate of P.

StCDPK5 confers resistance to late blight pathogen but increases susceptibility to early blight pathogen in potato via reactive oxygen species burst.

• Potato (Solanum tuberosum) calcium-dependent protein kinase (StCDPK5) has been shown to phosphorylate the N-terminal region of plasma membrane RBOH (respiratory burst oxidase homolog) proteins, and participate in StRBOHB-mediated reactive oxygen species (ROS) burst. The constitutively active form, StCDPK5VK, provides a useful tool for gain-of-function analysis of RBOH in defense responses. • StCDPK5- and StCDPK5VK-green fluorescent protein fusion proteins were predominantly targeted to the plasma membrane, and conditional expression of StCDPK5VK activated StRBOHA-D.

Calcium-dependent protein kinases regulate the production of reactive oxygen species by potato NADPH oxidase.

Reactive oxygen species (ROS) are implicated in plant innate immunity. NADPH oxidase (RBOH; for Respiratory Burst Oxidase Homolog) plays a central role in the oxidative burst, and EF-hand motifs in the N terminus of this protein suggest possible regulation by Ca(2+). However, regulatory mechanisms are largely unknown.

Nitrate reductase is responsible for elicitin-induced nitric oxide production in Nicotiana benthamiana.

Recent works have established a key role for nitric oxide (NO) in activating disease resistance in plants. Nitrate reductase (NR) is one of the enzymes that are capable of producing NO in plants. In a previous study, we reported that pathogen signals induce expression of NR genes in potato, suggesting the involvement of NR in NO production induced by pathogen signals.

Peroxynitrite generation and tyrosine nitration in defense responses in tobacco BY-2 cells.

Peroxynitrite (ONOO(-)) is a compound formed by reaction of superoxide (O(2) (-)) with nitric oxide (NO) and is expected to possess characteristics of both O(2) (-) reactivity and NO mobility in order to function as a signal molecule. Although there are several reports that describe the role of ONOO(-) in defense responses in plants, it has been very difficult to detect ONOO(-) in bioimaging due to its short half-life or paucity of methods for ONOO(-)-specific detection among reactive oxygen species or free radicals. Aminophenyl fluorescein (APF), a recently developed novel fluorophore for direct detection of ONOO(-) in bioimaging, was used for intracellular ONOO(-) detection.

Subcellular localization of Strboh proteins and NADPH-dependent O2(-)-generating activity in potato tuber tissues.

Rapid generation of reactive oxygen species (ROS) at the cell surface has been implicated in plant defence responses. Genetic evidence indicates that a plant NADPH oxidase (Rboh; respiratory burst oxidase homologue) is associated with oxidative burst. However, there is not enough physiological evidence of Rboh localization available yet.

Rewiring mitogen-activated protein kinase cascade by positive feedback confers potato blight resistance.

Late blight, caused by the notorious pathogen Phytophthora infestans, is a devastating disease of potato (Solanum tuberosum) and tomato (Solanum lycopersicum), and during the 1840s caused the Irish potato famine and over one million fatalities. Currently, grown potato cultivars lack adequate blight tolerance. Earlier cultivars bred for resistance used disease resistance genes that confer immunity only to some strains of the pathogen harboring corresponding avirulence gene.

Involvement of PPS3 phosphorylated by elicitor-responsive mitogen-activated protein kinases in the regulation of plant cell death.

Mitogen-activated protein kinase (MAPK) cascades play pivotal roles in plant innate immunity. Overexpression of StMEK1(DD), a constitutively active MAPK kinase that activates salicylic acid-induced protein kinase (SIPK) and wound-induced protein kinase (WIPK), provokes hypersensitive response-like cell death in Nicotiana benthamiana. Here we purified a 51-kD MAPK, which was activated in potato (Solanum tuberosum) tubers treated with hyphal wall elicitor of a plant pathogen, and isolated the cDNA designated StMPK1.

Nicotiana benthamiana gp91phox homologs NbrbohA and NbrbohB participate in H2O2 accumulation and resistance to Phytophthora infestans.

Active oxygen species (AOS) are responsible for triggering defense responses in plants. Respiratory burst oxidase homologs (rboh genes) have been implicated in AOS generation. We have isolated two rboh cDNAs, NbrbohA and NbrbohB, from Nicotiana benthamiana leaves.