236
S. Gleissberg et al.
l1li Kl\OTIED I STM I KNA I
•
LEAFY: PHA J TASTICA
Fig. 4. Line diagram showing expression of the KNOX
genesKNl andSTMl in the
shoot apical meristem, and
PRAN expression in developing leaf primordia. These
two expression patterns are
complementary in nature.
PO, incipient leaf primordium
expression pattern is complementary to SHOOTMERISTEMLESS (a KNOTTED1
like gene in Arabidopsis) mRNA accumulation, which is downregulated in lateral
organ primordia (Fig. 4; Waites et at. 1998). This expression pattern of PH ANTASTICA suggests that PHAN could be a negative regulator of SHOOTMERISTEMLESS. Support for the regulatory relationship of PHANTASTICA and KNOTTED1
was reported in maize recently (Schneeberger et at. 1998). These authors found
that a mutation resembling KNOTTEDI-Iike gain of function mutants (roughsheath
2) is caused by the failure to successfully downregulate KNOTTED1 and other related genes like ROUGHSHEATH1 in the leaf primordium. The rs2 mutation has
been reported to be at a PHAN-like locus in maize (Fig. 1D; Schneeberger et at.
1998). The leajbladeless1 (Ibll) mutation has leaves with only abaxial identity
(Timmermans et at. 1998). A direct or indirect role of Lbll to downregulate KNOTTED1 was also proposed. KNOTTED1 and its homologs are well known for their
function in leaf, meristem and compound leaf development (Jackson et at. 1994;
Sinha et at. 1993; Smith et at. 1992; Hareven et at. 1996; Janssen et al 1998; Chen
et at. 1997). Thus, intense analysis of PHANTASTICA, KNOTTED1, and their homologs, and interactions between these two classes of genes will provide insight
into fundamental developmental regulation in plants.
The possibility that homeobox genes can directly playa role in the establishment of ab-adaxiality was suggested recently (Tamaoki et at. 1997). Tobacco plants
S. Gleissberg et al.
l1li Kl\OTIED I STM I KNA I
•
LEAFY: PHA J TASTICA
Fig. 4. Line diagram showing expression of the KNOX
genesKNl andSTMl in the
shoot apical meristem, and
PRAN expression in developing leaf primordia. These
two expression patterns are
complementary in nature.
PO, incipient leaf primordium
expression pattern is complementary to SHOOTMERISTEMLESS (a KNOTTED1
like gene in Arabidopsis) mRNA accumulation, which is downregulated in lateral
organ primordia (Fig. 4; Waites et at. 1998). This expression pattern of PH ANTASTICA suggests that PHAN could be a negative regulator of SHOOTMERISTEMLESS. Support for the regulatory relationship of PHANTASTICA and KNOTTED1
was reported in maize recently (Schneeberger et at. 1998). These authors found
that a mutation resembling KNOTTEDI-Iike gain of function mutants (roughsheath
2) is caused by the failure to successfully downregulate KNOTTED1 and other related genes like ROUGHSHEATH1 in the leaf primordium. The rs2 mutation has
been reported to be at a PHAN-like locus in maize (Fig. 1D; Schneeberger et at.
1998). The leajbladeless1 (Ibll) mutation has leaves with only abaxial identity
(Timmermans et at. 1998). A direct or indirect role of Lbll to downregulate KNOTTED1 was also proposed. KNOTTED1 and its homologs are well known for their
function in leaf, meristem and compound leaf development (Jackson et at. 1994;
Sinha et at. 1993; Smith et at. 1992; Hareven et at. 1996; Janssen et al 1998; Chen
et at. 1997). Thus, intense analysis of PHANTASTICA, KNOTTED1, and their homologs, and interactions between these two classes of genes will provide insight
into fundamental developmental regulation in plants.
The possibility that homeobox genes can directly playa role in the establishment of ab-adaxiality was suggested recently (Tamaoki et at. 1997). Tobacco plants