65 °C for 15 min in 0.1X SSC and 0.1% SDS and then exposed
to Kodak XOMAT X-Ray film at −70 °C for 1 week.
2.5. Cloning of ERS1 promoter
Total DNA from young apple leaf was isolated according to
Dellaporta et al. (1983) and a genome walker library was
constructed using Universal genome walker kit (Clonetech). For
the isolation of ERS1 proximal promoter gene specific primers
from the 5′ region of ERS1 close to translational start site was
designed and used for PCR amplification using the genome
walker library as template. The amplified fragment was cloned
in plasmid pCR2.1-TOPO (Invitrogen, USA) and sequenced.
The search for conserved regulatory regions with other known
sequences was carried using http://www.dna.affrc.go.jp/htdocs/
PLACE/ a database of motifs found in cis-acting regulatory
DNA elements of vascular plants (Higo et al., 1999).
2.6. Statistical analysis
Each experiment was carried out under completely randomized
design with three replications repeated at least thrice. The
data were analyzed by student's unpaired t-test, and the
treatment mean values were compared at P≤0.05–0.001.