NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Proteolytic activity during senescence of plantsAlthough information has rapidly developed concerning the intracellular localization of plant proteins, relatively few reports concern the intracellular location of endo- and exo-proteolytic activities. Relatively few proteases have been purified, characterized, and associated with a specific cellular location. With the exception of the processing proteases involved in transport of proteins across membranes, little progress has yet been made concerning determination of in vivo products of specific proteases. Information on the turnover of individual proteins and the assessment of rate-limiting steps in pathways as proteins are turned over is steadily appearing. Since chloroplasts are the major site of both protein synthesis and, during senescence, degradation, it was important to show unambiguously that chloroplasts can degrade their own constituents. Another important contribution was to obtain evidence that the chloroplasts contain proteases capable of degrading their constituents. This work has been more tenuous because of the low activities found and the possibility of contamination by vacuolar enzymes during the isolation of organelles. The possible targeting of cytoplasmic proteins for degradation by facilitating their transport into vacuoles is a field which hopefully will develop more rapidly in the future. Information on targeting of proteins for degradation via the ubiquitin (Ub) degradation pathway is developing rapidly. Future research must determine how much unity exists across the different eukaryotic systems. At present, it has important implications for protein turnover in plants, since apparently Ub is involved in the degradation of phytochrome. Little information has been developed regarding what triggers increased proteolysis with the onset of senescence, although it appears to involve protein synthesis. Thus far, the evidence indicates that the complement of proteases prior to senescence is sufficient to carry out the observed protein degradation. This field of study has great practical implications, e.g. maintaining photosynthesis during seed-fill in order to obtain greater crop yields. The current use of stay green' variants in the populations of several crop plants to produce increased yields shows the potential for future development. The near future should see exciting discoveries in these areas of research that will have far reaching effects on the construction of transgenic plants for future research accomplishments and agricultural use.
Document ID
20040112167
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Huffaker, R. C.
(University of California Davis 95616)
Date Acquired
August 21, 2013
Publication Date
January 1, 1990
Publication Information
Publication: The New phytologist
Volume: 116
ISSN: 0028-646X
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Review, Academic
Non-NASA Center
Review
NASA Program CELSS
NASA Discipline Life Support Systems
NASA Discipline Number 61-10

Available Downloads

There are no available downloads for this record.
No Preview Available