Phloem parenchyma (PP) cells of Arabidopsis leaf veins trans-differentiate to become PP transfer cells (TCs) which are thought to aid phloem loading by facilitating unloading of photoassimilates into the apoplasm for subsequent energy-dependent uptake into the sieve element/companion cell (SE/CC) complex. We are using PP TCs in Arabidopsis as a genetic model to identify transcription factors putatively involved in coordinating the deposition of the wall ingrowth network. Detailed analysis of wall ingrowth deposition by confocal microscopy of modified pseudo-Schiff-propidium iodide-stained tissue shows that wall ingrowths are absent in PP cells of 5-day-old cotyledons but abundant in cotyledons at 10 days, and similarly absent in leaf 1 of 10-day-old seedlings but abundant in leaf 1 at 16 days. Using these observations, we have undertaken transcript profiling (RNA-Sequencing) of wall ingrowth deposition in PP TCs and identified 41 differentially expressed (FDR-corrected P values ≤0.05) transcription factors that are commonly up- or down-regulated when comparing 5-day vs 10-day cotyledons, 10-day vs 16-day leaf 1, and 10-day cotyledons vs 10-day leaf 1. Among them, the 22 transcription factors commonly up-regulated were characterized by members of the NAC-domain, MYB and ERF families. Several of the NAC-domain transcription factors, including the paralogs AtNAC56 and AtNAC18 have been identified as genes involved in secondary wall formation. We report results from co-expression network analysis to further refine a subset of transcription factors likely to participate in genetic regulation of wall ingrowth deposition and test these predictions by phenotypic analysis of relevant mutants.