Plant Molecular Biology 40: 397–408, 1999.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
MsJ1, an alfalfa DnaJ-like gene, is tissue-speciﬁc and transcriptionally
regulated during cell cycle
, Giovanni Mele, Donato Giannino and Domenico Mariotti
Istituto di Biochimica ed Ecoﬁsiologia Vegetali, CNR, Via Salaria Km 29300, 00016 Monterotondo Scalo (RM),
authors for correspondence)
Received 13 July 1998; accepted in revised form 5 February 1999
Key words: cell cycle, DnaJ, heat shock, Medicago sativa, molecular chaperones, transcriptional regulation
DnaJ-like proteins are molecular chaperones that regulate Hsp70 ATPase activity both in protein folding, assembly
and disassembly of protein complexes. Here we report the isolation of MsJ1, an alfalfa gene encoding a protein
homologous to cytosolic DnaJ-like proteins. MsJ1 was induced under heat-shock treatment in both leaves and
stems of adult plants. In the absence of heat shock MsJ1 expression was tissue-speciﬁc with the highest levels
of mRNA in roots and in embryonal structures. High levels of transcript were also detected in cotyledons where
active degradation of storage protein occurs. In synchronized alfalfa suspension-cultured cells the MsJ1 transcript
was actively expressed and showed a phase-speciﬁc modulation during cell cycle with a 2-fold induction in G2/M.
These ﬁndings suggest that DnaJ-like proteins play an active role in regulating normal cellular events like protein
degradation,morphogenesis and cell cycle progression.
Molecular chaperones have been deﬁned as ‘proteins
that bind to and stabilize an otherwise unstable con-
former of another protein and, by controlled binding
and release of the substrate protein, facilitate its cor-
rect fate in vivo, be it folding, oligomeric assembly,
transport to a particular subcellular compartment, or
disposal by degradation’ (Hendrick and Hartl, 1993).
Although most of these proteins are constitutively ex-
pressed, their synthesis is often signiﬁcantly increased
upon stress (Lindquist, 1986). Several heat-shock pro-
tein families have been identiﬁed in a wide range of
organisms (Gething and Sambrook, 1992; Hendrick
and Hartl, 1993). Among these, the folding and as-
sembly of protein complexeswithin the compartments
of eukaryotic cells have been found to be catalysed by
different members of the Hsp70 protein family (Hartl,
1996). The chaperone function of Hsp70 proteins is
thought to be regulated by members of the DnaJ-like
The GenBank accession numbers of the sequences reported in
this article are Z71997, AJ000995 and AF069507.
protein family, occurring through direct interaction of
different Hsp70 and DnaJ protein pairs which are pro-
posed to be speciﬁcally adapted to each other (Bond
and Schlesinger, 1987; Cyr et al., 1994).
DnaJ-like genes have been identiﬁed in organisms
ranging from yeast to plants and man (Blumberg and
Silver, 1991; Luke et al., 1991; Atencio and Yaffe,
1992; Bessoule, 1993; Preisig-Muller and Kindl,
1993; Zhu et al., 1993a, 1995; Caplan and Douglas,
1994; Cyr et al., 1994). Members of the DnaJ-like
protein family are structurally diverse and contain dif-
ferent combinations of three conserved domains. All
DnaJ-like proteins are characterized by a J-domain
which mediates interactions with Hsp70. A set of four
conserved cysteine and glycine residues resembling a
zinc-ﬁnger motif identiﬁes a DnaJ subfamily whose
members are closely related to the YDJ1 yeast protein.
A glycine-rich region varying in length is also present
in most of the cytosolic and mitochondrial eukaryotic
DnaJ-like proteins. Regions in the carboxyl terminus
of the protein are less conserved. They are proposed
to mediate interactions with polypeptides, suggesting
that different DnaJ-like proteins may have developed