PmNAC1 gene is induced by auxin and expressed in differentiating vascular cells in callus cultures of Passiflora

The plant-specific NAM/ATAF/CUC (NAC) transcription factors play critical roles in diverse developmental processes such as the establishment of the shoot apical meristem, lateral root formation, flowering time, senescence, abiotic stress and defense responses. NAC domain transcription factors may be regulated at the transcriptional level by environmental clues, such as hormone concentrations. Here we report the cloning of a Passiflora morifolia putative homolog to a gene encoding a NAC-domain transcription factor, PmNAC1. We have examined the expression patterns of this gene during in vitro callus induction and growth. We observed that the induction of transcript levels of PmNAC1 is correlated to increasing concentrations of 1-naphthalene acetic acid in the culture medium. Additionally, the results of in situ hybridization experiments indicated a dynamic spatial expression pattern for PmNAC1 during callus growth, coincidental with provascular tissue differentiation, especially with xylem cell specification.