Reference "Synthesis, processing and export of cytoplasmic endo-beta-1,4-xylanase from barley aleurone during germination"

Reference ID

8890

Title

Synthesis, processing and export of cytoplasmic endo-beta-1,4-xylanase from barley aleurone during germination

Source

The Plant journal : for cell and molecular biology, 2001, vol. 26, pp. 191-204

Authors (5)

Caspers-M-P	Lok-F
Sinjorgo-K-M	Nielsen-K-A
Cameron-Mills-V

Abstract

We have identified the major endo-beta-1,4-xylanase (XYN-1) in the aleurone of
germinating barley grain, and show that it is expressed as a precursor of Mr 61
500 with both N- and C-terminal propeptides. XYN-1 is synthesized as an inactive
enzyme in the cytoplasm, and only becomes active at a late stage of germination
when the aleurone ceases to secrete hydrolases. A series of processing steps,
mediated in part by aleurone cysteine endoproteases, yields a mature active
enzyme of Mr 34 000. Processing and extracellular release of the mature enzyme
coincide with the programmed cell death (PCD)-regulated disintegration of
aleurone cells. We discuss the significance of delayed aleurone cell-wall
degradation by endoxylanases in relation to the secretory capacity of the
aleurone, and propose a novel role for aleurone PCD in facilitating the export
of hydrolases.