Planta (2006) 225:89–102
DOI 10.1007/s00425-006-0332-y
123
ORIGINAL ARTICLE
CHRD, a plant member of the evolutionarily conserved YjgF
family, inXuences photosynthesis and chromoplastogenesis
Yael Leitner-Dagan · Marianna Ovadis · Amir Zuker ·
Elena Shklarman · Itzhak Ohad · Tzvi TzWra ·
Alexander Vainstein
Received: 19 March 2006 / Accepted: 8 May 2006
/ Published online: 15 July 2006
© Springer-Verlag 2006
Abstract Studies on the carotenoid-overaccumulat-
ing structures in chromoplasts have led to the charac-
terization of proteins termed plastid lipid-associated
proteins (PAPs), involved in the sequestration of
hydrophobic compounds. Here we characterize the
PAP CHRD, which, based on sequence homology,
belongs to a highly conserved group of proteins,
YER057c/YjgF/UK114, involved in the regulation of
basic and vital cellular processes in bacteria, yeast and
animals. Two nuclear genes were characterized in tomato
plants: one (LeChrDc) is constitutively expressed in
various tissues and the other (LeChrDi) is induced by
stress in leaves and is upregulated by developmental
cues in Xoral tissues. Using RNAi and antisense
approaches, we show their involvement in biologically
signiWcant processes such as photosynthesis. The quan-
tum yield of photosynthetic electron Xow in transgenic
tomato leaves with suppressed LeChrDi/c expression
was 30–50% of their control, non-transgenic counter-
parts and was ascribed to lower PSI activity. Transgenic
Xowers with suppressed LeChrDi/c also accumulated
up to 30% less carotenoids per unit protein as com-
pared to control plants, indicating an interrelationship
between PAPs and Xoral-speciWc carotenoid accumula-
tion in chromoplasts. We suggest that CHRD’s role in
the angiosperm reproductive unit may be a rather
recent evolutionary development; its original function
may have been to protect the plant under stress condi-
tions by preserving plastid functionality.
Keywords Chloroplast · Chromoplasts · Plastid ·
Stress · Tomato · YjgF protein
Abbreviations
PAP(s) Plastid lipid-associated protein(s)
TOPI Topoisomerase I
Introduction
Complex biochemical and structural processes deter-
mine the pathway of plastid biogenesis. Each speciWc
plastid accumulates a unique set of proteins/pigments,
which determine its functionality. Whereas chlorop-
lasts, which are responsible for photosynthesis, accu-
mulate components of the photosynthetic apparatus,
chromoplasts, which in many cases derive from them,
accumulate high levels of carotenoids and are primarily
responsible for attracting pollinators and seed dispers-
ers. In chromoplasts, several types of carotenoid-accu-
mulating structures have been revealed by EM:
Y. Leitner-Dagan and M. Ovadis contributed equally to this work
Y. Leitner-Dagan · M. Ovadis · A. Zuker · E. Shklarman ·
A. Vainstein (&)
The Robert H. Smith Institute of Plant Sciences and Genetics
in Agriculture, Faculty of Agricultural,
Food and Environmental Quality Sciences,
The Hebrew University of Jerusalem, P.O. Box 12,
Rehovot 76100, Israel
e-mail: vain@agri.huji.ac.il
I. Ohad
Department of Biological Chemistry,
The Hebrew University of Jerusalem,
Jerusalem 91014, Israel
T. TzWra
Department of Molecular, Cellular and Developmental
Biology, University of Michigan, Ann Arbor,
MI 48109, USA