Disruption of chloroplast biogenesis and plant development upon down‐regulation of a chloroplast processing enzyme involved in the import pathway

Autor: Gayle K. Lamppa, David Bringloe, Jiangxin Wan
Rok vydání: 1998
Předmět:
Zdroj: The Plant Journal. 15:459-468
ISSN: 1365-313X
0960-7412
DOI: 10.1046/j.1365-313x.1998.00224.x
Popis: Summary Typically, nuclear-encoded chloroplast proteins are synthesized as precursors and require proteolytic processing upon import before their assembly into functional complexes within the organelle. A cDNA encoding a chloroplast processing enzyme (CPE), which was originally identified as a protease that cleaves the precursor for the major light-harvesting chlorophyll binding protein (preLHCP), was introduced into the tobacco genome in an antisense orientation to investigate the role of the enzymein vivo. The presence of the antisense-CPE gene resulted in chlorotic leaves, and retarded shoot and root growth. The introduction of the antisense-CPE gene disrupted the normal pattern of plastid division. Chloroplast numbers in cotyledon and first leaf cells were reduced 25% compared to the control plants. Chloroplasts contained fewer thylakoids and large starch grains, the latter an indication of a change in carbon flux. CPE levels and activity were significantly lower in stromal extracts in the transgenic plants. Interestingly,in vitroimport of precursor proteins was defective. Most of the preLHCP remained on the exterior of the organelle, and only a small fraction of preRBCA was imported, suggesting that a change in CPE levels can influence translocation across the envelope. Ourin vivoresults support the conclusion that CPE plays a critical role during chloroplast biogenesis, and that the pleiotropic effects of CPE down-regulation reflect its function as a general stromal processing peptidase as part of the import machinery. Furthermore, these findings indicate the importance of regulating the expression of components of the import machinery for normal plant development.
Databáze: OpenAIRE
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