The myco-heterotroph, Arachnitis uniflora, has a unique association with arbuscular mycorrhizal fungi

DOMÍNGUEZ, L.; MELVILLE, L.; SÉRSIC, A.; FACCIO, A; PETERSON, L.

BOTANY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Año: 2009 vol. 87 p. 1198 - 1208

1916-2790

<!-- /* Font Definitions */ @font-face {font-family:"MS Mincho"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-alt:"Arial Unicode MS"; mso-font-charset:128; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:fixed; mso-font-signature:1 134676480 16 0 131072 0;} @font-face {font-family:"@MS Mincho"; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:128; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:fixed; mso-font-signature:1 134676480 16 0 131072 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"MS Mincho"; mso-ansi-language:EN-US; mso-fareast-language:JA;} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Abstract Achlorophyllous plants that are dependent on an association with fungi linked to photosynthetic plants for their carbon source are known as myco-heterotrophs.  Arachnitis uniflora, a monotypic member of the monocotyledonous family Corsiaceae, fits this category as it relies on a glomalean fungus belonging to Glomus Group A for carbon acquisition. Although basic structural features of root colonization have been reported for A. uniflora, the nutrient exchange interface has not been studied. This is the first study to use confocal microscopy, transmission electron microscopy, and  cytochemical procedures to study the interface between a glomalean fungus and the roots of a myco-heterotrophic species. Results showed that arbuscules are never formed,  and the ‘vesicles in bundles’ reported earlier are unlike typical glomalean vesicles in that they form in clusters by the enlargement of hyphal branches and have a complex multi-layered wall. The thick inner wall layer consists primarily of β-1,3 glucans (callose), and is surrounded by a thin outer layer of chitin. Each structure is surrounded by host cell wall material and a perifungal membrane suggesting that an involvement in nutrient exchange. The cytoplasm contains a complex of small β-1,3 glucan-containing vacuoles, lipid bodies, endobacteria, and many nuclei. These structures enlarge to occupy most of the cortical cell volume and then degrade releasing lipids and other materials into the host cell. We suggest that these structures should not be equated with typical glomalean vesicles but are unique structures which may be involved, along with the hyphal coils, in nutrient acquisition by the host.