Phenolic metabolites of Ceratocystis minor from laboratory cultures and their effects on transpiration in loblolly pine seedlings

Abstract

Several low molecular weight phenolic metabolites of Ceratocystis minor (Hedgcock) Hunt, a blue-stain fungus of loblolly pine, were isolated from cultures grown on 2.5% malt-extract liquid medium. The most abundant compounds were 6,8-dihydroxy-3-hydroxymethyl isocoumarin and 6,8-dihydroxy-3-methyl isocoumarin. Two unknown phenolic compounds were also isolated. Solutions of these fungal metabolites stimulated transpiration in loblolly pine seedlings when administered through the cut stem. Rates of water loss were doubled within 24 h after treatment with isocoumarin solutions. Administration of raw or sterile fungal culture (in liquid medium) on the other hand produced a small but significant inhibition of water loss shortly after treatment. Reduction in transpiration after treatment with fungal culture probably is the result of partial tracheid blockage by as yet unidentified fungal products. Effects of metabolites of C. minor on the water relations of loblolly pine are discussed in terms of a possible mutualistic association between C. minor and the southern pine beetle, Dendroctonus frontalis Zimmermann.

The Role of Phytopathogenicity in Bark Beetle–Fungus Symbioses: A Challenge to the Classic Paradigm

“…The first hypothesis suggests that colonization of the tree by virulent fungi leads directly to tree death, primarily by blocking water conduction in the xylem (56,70). The fungi do not appear to produce toxins (25,34). The second hypothesis proposes that fungi lead indirectly to tree death by stimulating induced defenses in the phloem, which ultimately results in their exhaustion, allowing bark beetles to invade (60).…”

The chemistry of the blue stain fungi. Part 3. Some metabolites of Ceratocystisminor (Hedgcock) Hunt

“…Compound 6 presumably arises by acetylation of the enolic hydroxyl of 5 and 1,6-addition of acetic anhydride to the unsaturated carbonyl system. Diacetylacetoxyceratenolone (6) crystallizes from Skellysolve B as colorless prisms, mp 103-104°C. Figure 1 is a computer generated perspective drawing of the final X-ray model of diacetylacetoxyceratenolone (6).…”

“…Diacetylacetoxyceratenolone (6) crystallizes from Skellysolve B as colorless prisms, mp 103-104°C. Figure 1 is a computer generated perspective drawing of the final X-ray model of diacetylacetoxyceratenolone (6). ' Ceratenolone represents a new structural type among natural products.…”

“…The previously reported metabolite of C. minor, 6 , s -dihydroxy -3 -methy lisocoumarin (2), was isolated and identified by comparison of its spectral properties and those of its diacetyl derivative 7 with those reported (4-6). Four related methylisocoumarins were also isolated.…”

“…It was postulated that the blue stain associated with the fungal infection might be due to metal complexes of compound 1 (1). Since 2,3-dihydroxybenzoic acid was not reported as a metabolite of C. minor (4,6), and since this fungus stains pine most rapidly, we decided to reexamine the metabolites produced by the fungus. The metabolites reported earlier (4-6), 6,8-dihydroxy-3-methylisocoumarin (2), 6,8-dihydroxy-3-hydroxymethylisocoumarin (3), and 3,6,8-trihydroxy-a-tetralone (4), although phenolic in nature, do not contain the 2,3-dihydroxybenzoyl unit found in many strongly iron-chelating compounds (7) often referred to as siderophores (8).…”