Abstract:

Plant peptide hormones are small cleavage products of precursor peptides. A peptide
hormone gene named MdCEP1 was cloned from Malus × domestica‘Royal Gala’. The mechanism of
MdCEP1 on the growth and development of apple roots was discussed. The Open Reading Frame（ORF）
of MdCEP1 contained 366 bp，encoding 121 amino acid residues. Phylogenetic tree indicated that
MdCEP1 had the highest evolutionary relationship with PbCEP1 from pear. The qRT-PCR analysis
indicated that MdCEP1 had higher expression levels in apple root and stem compared with those in fruit and leaves. Additionally，MdCEP1 expression was negatively regulated by auxin concentration. The
synthetic peptide MdCEP1pHyp could inhibit the development of the root system of Arabidopsis
significantly. The main root was short and the number of lateral roots decreased. The ectopic expression of
MdCEP1 in Arabidopsis also showed a phenotype of reduced taproot and reduced number of lateral roots.
qRT-PCR analysis showed that the auxin related genes were significantly down regulated in exogenous
MdCEP1pHyp treatment and over expression of MdCEP1 in Arabidopsis. The results indicated that
MdCEP1 played a negative role in the growth and development of apple roots.

Key words: apple, peptide hormone, MdCEP1, root growth and development