Phytoalexin

About: Phytoalexin is a research topic. Over the lifetime, 1161 publications have been published within this topic receiving 63405 citations. The topic is also known as: phytoalexins.

Differential Elicitation Activities of Fractions from Phytophthora Spp. On Several Host-Plants

Abstract: Early observations suggested that neutral polysaccharides from parasitic fungi could be universal elicitors of plant defence reactions [1]. However, more recent findings have indicated that unsaturated fatty acids and lipoconjugates are the active elicitors of phytoalexin accumulation in potato tubers [2]. But arachidonic and eicosapentaenoic acids are not universal elicitors either: they induce phytoalexin accumulation in potato and pepper, but not in twelve other plant species surveyed, including other Solanaceae, tobacco and tomato [3].

Chitooligosaccharide elicitor and oxylipins synergistically elevate phytoalexin production in rice.

Abstract: KEY MESSAGE We show that in rice, the amino acid-conjugates of JA precursor, OPDA, may function as a non-canonical signal for the production of phytoalexins in coordination with the innate chitin signaling. The core oxylipins, jasmonic acid (JA) and JA-Ile, are well-known as potent regulators of plant defense against necrotrophic pathogens and/or herbivores. However, recent studies also suggest that other oxylipins, including 12-oxo-phytodienoic acid (OPDA), may contribute to plant defense. Here, we used a previously characterized metabolic defense marker, p-coumaroylputrescine (CoP), and fungal elicitor, chitooligosaccharide, to specifically test defense role of various oxylipins in rice (Oryza sativa). While fungal elicitor triggered a rapid production of JA, JA-Ile, and their precursor OPDA, rice cells exogenously treated with the compounds revealed that OPDA, rather than JA-Ile, can stimulate the CoP production. Next, reverse genetic approach and oxylipin-deficient rice mutant (hebiba) were used to uncouple oxylipins from other elicitor-triggered signals. It appeared that, without oxylipins, residual elicitor signaling had only a minimal effect but, in synergy with OPDA, exerted a strong stimulatory activity towards CoP production. Furthermore, as CoP levels were compromised in the OPDA-treated Osjar1 mutant cells impaired in the oxylipin-amino acid conjugation, putative OPDA-amino acid conjugates emerged as hypothetical regulators of CoP biosynthesis. Accordingly, we found several OPDA-amino acid conjugates in rice cells treated with exogenous OPDA, and OPDA-Asp was detected, although in small amounts, in the chitooligosaccharide-treated rice. However, as synthetic OPDA-Asp and OPDA-Ile, so far, failed to induce CoP in cells, it suggests that yet another presumed OPDA-amino acid form(s) could be acting as novel regulator(s) of phytoalexins in rice.

Accumulation and Antifungal Spectrum of 4'-Methoxyaucuparin as a New Phytoalexin in Rhaphiolepis umbellata Makino

Abstract: Accumulation and antifungal activity of a newly isolated phytoalexin, 4'-methoxyaucuparin, were described. The phytoalexin was accumulated in the leaves of Rhaphiolepis umbellata Makino inoculated with Pestalotiopsis sp. or Entomosporium mespili. Accumulation of 4'-methoxyaucuparin also occurred with treatment of 10-3M NaN3 or HgCl2 as abiotic elicitors. Of the elicitors tested, HgCl2 was found to be the most effective, being able to induce 4'-methoxyaucuparin at the concentration of 4, 385μg g-1 fresh weight. The inhibitory action of 4'-methoxyaucuparin against Pestalotiopsis sp., pathogenic fungus of R. umbellata, was weaker than that against non pathogenic fungi.