Questions and Answers about BIOLOGY

by Ken Miller and Joe Levine

QUESTION: Do plant cells contain lysosomes? Page 179 of the text doesn't clarify this.. [from Loren, a teacher in Texas]

Ha! You've put your finger on a messy little squabble among plant biologists that has gone on for years.

Current evidence suggests that "YES," some plant cells do contain lysosomes.

I did not flatly state that plant cells contain lysosomes because many cell biologists claim that they do not, and it was possible that such a flat statement would be considered an "error" by many teachers. However, there is emerging evidence that, in fact, they do. Here's a paper from the Journal "Plant Cell," pointing out the existence of an organelle in a plant cell that meets every criterion of a lysosome:

"Barley Aleurone Cells Contain Two Types of Vacuoles: Characterization of Lytic Organelles by Use of Fluorescent Probes." Sarah J. Swansona, Paul C. Bethkea, and Russell L. Jones . Plant Cell, Vol. 10, 685-698, May 1998

Here's a passage from the paper:

" The existence of lysosomes in plants has long been debated (see, e.g., Moriyasu and Ohsumi 1996 ). Matile 1975 recognized that catabolic enzymes were essential for sustained biological activity and that these enzymes must be compartmentalized to prevent their indiscriminate hydrolysis of biopolymers. He proposed that plant proteases, nucleases, phosphatases, and other degradative enzymes were constituents of a "lytic compartment," a compartment that included the extracellular space, vacuoles, and other organelles containing lytic enzymes. With improved techniques for vacuole isolation, it became clear that many plant vacuoles contain enzymes found in animal lysosomes (Matile 1978 ; Wink 1993 ). Plant vacuoles were therefore seen as fulfilling the role of the animal lysosomal system (Boller and Wiemken 1986 ). "

This is just one paper of many reporting plant cell lysosomes. The first such report appeared more than 30 years ago: Matile (1968) "Lysosomes of root tip cells in corn seedlines." Planta 79: 181-196.

So, the answer to your question seems to be "yes," but it remains a controversial one.

Ken Miller (10/11/04)

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