Abstract text: Arabinogalactan-proteins (AGPs) are cell-surface glycoproteins linking cell wall architecture to extracellular signaling; yet their developmental roles remain unclear. We performed RNA-seq on Arabidopsis galt2-9 octuple mutants lacking all eight hydroxyproline-O-galactosyltransferases required for AGP glycosylation, profiling seedlings, flowers, and siliques. Seedlings showed modest changes (646 DEGs), young flowers exhibited intermediate reprogramming (1,466 DEGs), activating pollen tube guidance and stress signaling. Young siliques displayed dramatic reprogramming (5,856 DEGs), strongly inducing defense and cell wall programs. Siliques achieved near-complete transcriptional compensation at maturity (99.97% normalization), driven by massive upregulation of ethylene response factors, receptor kinases, and WRKY transcription factors, whereas flowers accumulated emergent defects in pollen maturation genes. Co-expression network analysis identified distinct AGP networks with AGP5 co-expressed with stress and cell wall genes (GSTF6/7, WRKY41 and RLP28) in seedlings, while AGP13/14 was co-expressed with wall remodeling genes. In young flowers, AGP5 was co-expressed with receptor-mediated defense genes (CHI, PNP-A, RLP23), and pollen-related AGP6/11 associated with reproductive modules (VGDH1, PRK2A, RALFL4). In young siliques, AGP2/23 was co-expressed with transport, metabolism, and defense-related circuits. These results demonstrate that AGP glycosylation is a critical, organ-and age-dependent coordinator of cell wall integrity and reproductive transitions, triggering transcriptional compensation mechanisms essential to plant development.