Plant Molecular Biology 42: 765–773, 2000.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Tomato contains homologues of Arabidopsis cryptochromes 1 and 2
, Luciano Ninu
, Floriana Flamma
, James L. Weller
, Richard E. Kendrick
and Giovanni Giuliano
Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA), Innovation Dept., Casaccia Research Center,
PO Box 2400, Roma 00100AD, Italy (
author for correspondence);
Laboratory of Plant Physiology, Research
School of Experimental Plant Sciences, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen,
Received 29 September 1999; accepted in revised form 10 January 2000
Key words: blue light photoreceptors, gene duplication, Solanum lycopersicum
Cryptochromes are blue light photoreceptors found in both plants and animals. They probably evolved from pho-
tolyases, which are blue/UV-light-absorbing photoreceptors involved in DNA repair. In seed plants, two different
cryptochrome (CRY) genes have been found in Arabidopsis and one in Sinapis, while three genes have been
found in the fern Adiantum. We report the characterisation of tomato CRY genes CRY1 and CRY2.Theymap
to chromosomes 4 and 9, respectively, show relatively constitutive expression and encode proteins of 679 and 635
amino acids, respectively. These proteins show higher similarity to their Arabidopsis counterparts than to each
other, suggesting that duplication between CRY1 and CRY2 is an ancient event in the evolution of seed plants.
The seed plant cryptochromes form a group distinct from the fern cryptochromes, implying that only one gene
was present in the common ancestor between these two groups of plants. Most intron positions in CRY genes from
plants and ferns are highly conserved. Tomato cry1 and cry2 proteins carry C-terminal domains 210 and 160 amino
acids long, respectively. Several conserved motifs are found in these domains, some of which are common to both
types of cryptochromes, while others are cryptochrome-type-speciﬁc.
Blue light is perceived by plants through a series
of photoreceptors, including phytochrome A (Poppe
et al., 1998), Nph1/phototropin (Christie et al., 1998),
and the cryptochromes (Cashmore et al., 1999). This
last group belongs to a ubiquitous class of blue light
photoreceptors, found in higher and lower plants (Ah-
mad et al., 1993; Batschauer, 1993; Hoffman et al.,
1996; Lin et al., 1996; Kanegae and Wada, 1998),
insects (Emery et al., 1998) and mammals (Thresher
et al., 1998; van der Horst et al., 1999). In all organ-
isms studied, cryptochromes are involved in the con-
trol of circadian timing (Emery et al., 1998; Somers
The nucleotide sequence data reported will appear in the EMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession numbers AF130423 (CRY1 cDNA), AF130424 (CRY1
gene), AF130425 (CRY2 cDNA) and AF130426 (CRY2 gene).
et al., 1998; Thresher et al., 1998; Ceriani et al.,
1999; van der Horst et al., 1999). In Arabidopsis
they are also involved in a related phenomenon, the
control of ﬂowering time by photoperiod (Guo et al.,
1998; Mockler et al., 1999). Additionally, plant cryp-
tochromes are involved in phototropic response (Ah-
mad et al., 1998a) and in photomorphogenetic events
like the inhibition of seedling and internode elongation
and the biosynthesis of anthocyanins (Ahmad et al.,
1993, 1995; Lin et al., 1998; Ninu et al., 1999).
Cryptochromes have most likely evolved from
photolyases, another class of blue-UV-light-absorbing
ﬂavoproteins with a distinct function: they are in-
volved in the photoreactivation of UV-damaged DNA.
Photolyases contain two chromophores, one being a
ﬂavin and the other one either a pterin or a deazaﬂavin.
The evolution of cryptochromes from photolyases has
probably occurred twice, since plant cryptochromes