Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 11

What's Happening Researchers have discovered a group of plant proteins that are related to the exocyst proteins in yeast (The Plant Cell 20 (2008): 1330). Explain how the following observations made by these researchers suggest that these plant proteins form a tethering complex similar to the exocyst complex of yeast and mammals.
(a)Following size fractionation of plant protein extracts, antibodies recognizing each of several different plant exocyst proteins bind to the same high-molecular-weight protein fraction.
(b)Mutations in four of the proteins each causes defective pollen germination.
(c)Plants lacking more than one of these proteins have more serious defects in pollen germination than plants lacking only one.
(d)The exocyst proteins all co-localize at the growing tip of elongating pollen cells.
(e)Pollen cells of plants with mutations in exocyst genes are defective in tip growth or germinating pollen cells.