title: Calcium oxalate crystals: an integral component of the Sclerotinia sclerotiorum/Brassica carinata pathosystem.
abstract: Oxalic acid is an important virulence factor for disease caused by the fungal necrotrophic pathogen Sclerotinia sclerotiorum, yet calcium oxalate (CaOx) crystals have not been widely reported. B. carinata stems were infected with S. sclerotiorum and observed using light microscopy. Six hours post inoculation (hpi), CaOx crystals were evident on 46% of stem sections and by 72 hpi on 100%, demonstrating that the secretion of oxalic acid by S. sclerotiorum commences before hyphal penetration. This is the first time CaOx crystals have been reported on B. carinata infected with S. sclerotiorum. The shape of crystals varied as infection progressed. Long tetragonal rods were dominant 12 hpi (68% of crystal-containing samples), but by 72 hpi, 50% of stems displayed bipyramidal crystals, and only 23% had long rods. Scanning electron microscopy from 24 hpi revealed CaOx crystals in all samples, ranging from tiny irregular crystals (< 0.5 μm) to large (up to 40 μm) highly organized arrangements. Crystal morphology encompassed various forms, including tetragonal prisms, oval plates, crystal sand, and druses. Large conglomerates of CaOx crystals were observed in the hyphal mass 72 hpi and these are proposed as a strategy of the fungus to hold and detoxify Ca2+ions. The range of crystal morphologies suggests that S. sclerotiorum growth and infection controls the form taken by CaOx crystals.
authors: School of Plant Biology, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
authors: Margaret B
authors: MB
authors: Uloth
authors: Centre for Microscopy, Characterisation and Analysis, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
authors: Peta L
authors: PL
authors: Clode
authors: School of Plant Biology and The UWA Institute of Agriculture, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
authors: Ming Pei
authors: MP
authors: You
authors: School of Plant Biology and The UWA Institute of Agriculture, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
authors: Martin J
authors: MJ
authors: Barbetti
mesh_terms: D001203:Ascomycota / Q000737:chemistry / Q000378:metabolism / Q000472:pathogenicity*; D001937:Brassica / Q000737:chemistry / Q000378:metabolism / Q000382:microbiology*; D002129:Calcium Oxalate / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D025301:Hyphae / Q000737:chemistry / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology
chemical_list: D002129:Calcium Oxalate