Sequencing and annotation of the evergrowing locus in peach [Prunus persica (L.) Batsch] reveals a cluster of six MADS-box transcription factors as candidate genes for regulation of terminal bud formation

Buds are specialized structures that protect fragile meristematic regions during dormancy and are part of the mechanism that plants use to survive unfavorable environmental conditions such as low temperature or dessication stress. The evergrowing (evg) mutant of peach [Prunus persica (L.) Batsch] does not form terminal vegetative buds in response to dormancy-inducing conditions such as short days and low temperatures, and the terminal meristems maintain constant growth (leaf addition and internode elongation). We genetically mapped the evg trait and identified the corresponding genomic region in a wild-type genome. We sequenced and annotated the 132-kb region. Nineteen genes were predicted to be in the sequenced region. Ten of the predicted genes were demonstrated to be expressed in the wild-type germplasm but six of these were not expressed in mutant tissues. These six genes are a cluster of MIKC-type MADS-box transcription factors similar to genes from Ipomoea batatas and Solanum tuberosum MADS-box, which also regulate meristem growth in vegetative tissues. A 41,746-bp deletion is present in this region of the mutant genome which results in the loss of all or part of four of the six MADS-box genes. The six MADS-box genes that are not expressed in the mutant are candidates for the regulation of growth cessation and terminal bud formation in peach in response to dormancy-inducing conditions and have been named dormancy-associated MADS-box (DAM) genes.