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The role of kinetosome-associated organelles in the attachment of encysting secondary zoospores ofSaprolegnia ferax to substrates

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Summary

Electron and fluorescence microscopy were used to identify organelles involved in attachment of secondary zoospores ofSaprolegnia ferax as they were transformed into secondary cysts. When secondary zoospores were exposed to 1.0% peptone in the absence or presence of a substrate, they began to encyst. If substrates were present when encystment was induced, the groove surface of the secondary zoospores adhered to them. The first event in attachment was secretion of contents of the kinetosome-associated organelle (K-body), which was typically oriented with the tubule-filled cavity positioned toward the cell surface of the groove region in the zoospore. The tubules which contained carbohydrates became coarsely granular, the matrix became more fibrous, and the shell remained along the membrane concavity that was formed as the K-body fused with the plasma membrane.

Five minutes later, a cyst coat appeared, and cysts were not readily dislodged from a substrate. The concavity was no longer found, presumably because it had evaginated; but a layered pad of adhesion material was between the cyst coat and substrate. The layers of the adhesion pad corresponded to the structure of the matrix of K-bodies. As with the tubules of the K-body, the coarsely granular portion at the edge of the pad stained for carbohydrates. Similarly, the lectins WGA and GS-II labeled with fluorescein stained the rim of the adhesion pad on cysts, indicating the presence of glycoconjugates containing N-acetylglucosamines. Because globular areas near the kinetosomes and groove of zoospores (where K-bodies were located) also bound WGA and GS-II, K-bodies contained the same carbohydrates as the adhesion pad. We conclude that K-bodies function in the attachment of encysting zoospores to substrates as the cell differentiates. The tubular portion of the K-body matrix contains carbohydrates which might assist in the adhesion process.

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Abbreviations

D:

dictyosome

EV:

encystment vesicle

F:

flagellum

C:

cyst

CC:

cyst coat

Con A:

concanavalin A

GS-II:

Griffonia simplicifolia lectin

K:

K-body

Kt:

kinetosome

M:

mitochondria

N:

nucleus

NB:

nuclear beak

PC:

peripheral cisterna

PV:

peripheral vesicle

S:

shell region of K-body matrix

SBA:

soybean agglutinin

R 3:

anteriorly directed triplet rootlet

R 8:

posteriorly directed octet rootlet

WEV:

water expulsion vacuole

WGA:

wheat germ agglutinin

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Authors and Affiliations

  1. Department of Botany, Miami University, Oxford, Ohio

    L. P. Lehnen Jr. & Martha J. Powell

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  1. L. P. Lehnen Jr.
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  2. Martha J. Powell
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Lehnen, L.P., Powell, M.J. The role of kinetosome-associated organelles in the attachment of encysting secondary zoospores ofSaprolegnia ferax to substrates. Protoplasma 149, 163–174 (1989). https://doi.org/10.1007/BF01322988

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