“…The thioninlike family of small cysteine-rich proteins provides a striking example: A single MYB-dependent member was identified by microarray analysis (Leydon et al, 2013), while RNA-seq analysis identified 24 family members whose expression was significantly decreased in myb triple-mutant pollinations compared with the wild type ( Figure 6). MYB-dependent secreted proteins were of particular interest because recent analysis documented the rich diversity of the tobacco (Nicotiana tabacum) pollen tube secretome (Hafidh et al, 2016) and suggested that the pollen tube and the synergid cell (Punwani et al, 2007;Liu et al, 2015) both evolved highly active secretory systems. Interestingly, genes that require MYB transcription factors for expression in the pollen tube are enriched for secreted proteins including two alpha carbonic anhydrases ( Figures 4O to 4T), 11 endopeptidases, 22/28 thionins in the CRP2460 gene family (Figure 6), 19/98 S-protein homologs (Ride et al, 1999), two cysteine-rich secretory, antigen 5, and pathogenesisrelated 1 proteins (CAP; AT3G09590 and AT5G02730), and four rapid alkalinization factors (AT2G32835, AT2G32788, AT2G32785, and AT1G60815; Supplemental Data Sets 8 and 9).…”