Abstract:

A total of 18 Auxin efflux carrier protein PIN were identified from the apple genome. We
further systematically analyzed its physical and chemical characteristics，gene structures，evolutionary
relationships and promoter elements. Results showed that the MdPIN gene family contained 1–14 exons
and 0–13 introns；3–10 conserved motifs existed in the MdPIN proteins；MdPIN and AtPIN proteins
were highly homologous and they could be classified into G1，G2 and G3 according to its homology.
Tissue-specific expressions indicated that 18 MdPIN genes had significantly different expression patterns
in different organs or tissues of different genotypes. A candidate gene MdPIN15 was separated and cloned
from axillary bud of Nagafu 2. The open reading frame was 1 869 bp，and it encoded 622 amino acids. Real-time quantitative PCR showed that the the highest transcription level of MdPIN15 was found in the
shoot tips，the second in the axillary buds，and the lowest in the flower buds. Exogenous GR24 and
Lovastatin（LVS）treatments reduced MdPIN15 expression，while it was increased by exogenous 6-BA and
decapitation treatments. It seems to be possible that MdPIN15 could play a vital role in the axillary bud
burst mediated by cytokinin（CK），indole-3-acetic acid（IAA）and strigolactone（SL）.

Key words: appple, PIN, buds burst, bioinformatic, gene expression