PpACS1b, a pear gene encoding ACC synthase, is regulated during fruit late development and involved in response to salicylic acid

• We isolated a gene encoding an ACC synthase from pear and designated it as PpACS1b.
• The PpACS1b gene contains three introns.
• The deduced PpACS1b protein was grouped into the type-2 plant ACS subfamily.
• PpACS1b were developmentally regulated during fruit ripening and senescence.
• PpACS1b expression in pear fruit was regulated by salicylic acid and ethylene.

ACC synthase is the rate-limiting enzyme during ethylene biosynthetic pathway. Using PCR amplification, a gene encoding an ACC synthase was isolated from pear (Pyrus pyrifolia) and consequently designated as PpACS1b. This gene was shown to contain three introns with typical GT/AG boundaries defining the splice junctions. The deduced PpACS1b protein contains the conserved features of ACSs: Aminotransferases class-I pyridoxal-phosphate attachment site and aminotransferase class I and II domain. Phylogenetic analyses clearly demonstrated that PpACS1b has the highest homology with pear PbACS1b and PcACS1b. Moreover, the PpACS1b was grouped into type-2 plant ACS subfamily based on its conserved domain and phylogenetic status. PpACS1b transcripts were mainly detected in young leaves, with low signal being detected in anthers and fruit. In particular, expression of PpACS1b was developmentally regulated during fruit ripening and senescence. Further study demonstrated that PpACS1b expression in pear fruit was regulated by salicylic acid and ethylene. Given all the above results together, these data suggested that PpACS1b might be involved in the response to SA and ethylene during pear fruit late development.