Contributes to cell wall structure in root hairs and seeds, especially in phosphate (Pi) deprivation conditions or in the presence of ethylene (PubMed:28138059, PubMed:28837399). Particularly important in maternal tissues (pericarps and seed coats) during seed development, especially under stress conditions (PubMed:28138059, PubMed:30673938). Confers thermotolerance in seed germination rate (PubMed:30673938). Root hair and seed specific expression (PubMed:19448035, PubMed:28138059, PubMed:28837399). Also observed in other tissues including siliques, roots and flowers (PubMed:28138059, PubMed:28837399). In roots, observed in root tips and elongating regions of the primary and lateral roots, especially in root hairs and collet hairs (PubMed:28138059). In reproductive organs, present in fruits and anthers (mostly in young anthers) (PubMed:28138059). Later detected in the pericarps and receptacles during maturation of siliques (PubMed:28138059). In siliques, expressed in the embryo (from the initial globular to mature stages), funiculus and seed coat (in the transparent inner integument) (PubMed:28138059). Expression levels are coordinated with root hair cell elongation (PubMed:28837399). Accumulates in root hairs within five days under phosphate (Pi) deficient conditions (at protein level). No visible phenotype under normal conditions (PubMed:28138059). Short and abnormally shaped root hairs due to the suppression of cell growth and cell death, and withered seeds, both having a tendency to necrotize and thick cell walls with abnormal structure in phosphate (Pi) deficient conditions or after ethylene treatment (PubMed:28138059, PubMed:28837399). Production of dark brown shrunken seeds unable to germinate, especially in low humidity (PubMed:30673938). Belongs to the plant proline-rich protein superfamily.