Phosphate transfer from maternal tissue to embryo

Many nutrients move through the plant body via the phloem. The developing embryo, which depends on the maternal plant for its nutrients, is not directly (symplastically) connected to maternal tissues, so nutrients must be exported across membranes to reach the embryo. PHO1 was identified previously as a phosphate exporter from roots cells into the apoplastic space for loading into the xylem (therefore, pho1 mutants are deficient in phosphate in the shoots). Vogiatzaki et al. showed that PHO1 and its closest homologue PHOH1 are expressed in the chalazal seed coat (CZSC), a specialized tissue involved in nutrient transfer. Using mutant and cell-specific knock-down or complementation methods, the authors showed that, “PHO1 expression in the CZSC is important for the transfer of P from the seed coat to the embryo in developing seeds.” (Summary by Mary Williams) Curr. Biol. 10.1016/j.cub.2017.08.026

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