Reference "Subpopulations of chloroplast ribosomes change during photoregulated development of Zea mays leaves: ribosomal proteins L2, L21, and L29"

Reference ID

7648

Title

Subpopulations of chloroplast ribosomes change during photoregulated development of Zea mays leaves: ribosomal proteins L2, L21, and L29

Source

Proceedings of the National Academy of Sciences of the United States of America, 1999, vol. 96, pp. 8997-9002

Authors (4)

Zhao-Y-Y	Xu-T
Zucchi-P	Bogorad-L

Abstract

Seedlings grown in darkness, i.e., etiolated seedlings, lack chlorophyll and
most other components of the photosynthetic apparatus. On illumination, the
plastids become photosynthetically competent through the production of
chlorophylls and proteins encoded by certain chloroplast and nuclear genes.
There are two types of photosynthetic cells in leaves of the C4 plant maize:
bundle sheath cells (BSC) and adjacent mesophyll cells (MC). Some proteins of
the maize photosynthetic machinery are solely or preferentially localized in MC
and others in BSC. A particular gene may be photoregulated up in one cell type
and down in the other. Transcripts of the nuclear gene rpl29, encoding the
chloroplast ribosomal protein L29, increase in abundance about 17-fold during
light-induced maturation of plastids. There is about 1.5 times more L29 protein
in ribosomes of greening leaves than in ribosomes of unilluminated leaves; the
L29 contents of MC and BSC are about the same. However, L21 is present about
equally in plastid ribosomes of unilluminated and illuminated seedlings. In
contrast to both L29 and L21, the fraction of the ribosome population containing
L2 is about the same in MC and BSC of etiolated leaves but, on illumination, the
proportion of the ribosome population with L2 increases in BSC but not in MC.
The existence of different subpopulations of plastid ribosomes-e.g., those with
and without L21 and/or L29 during development-evokes interesting, but as yet
unanswered, questions about the roles of different types of ribosomes in
differentiation.