The ACID PHOSPHATASE 1 regulates Pi stress adaptation by maintaining
intracellular Pi homeostasis
Abstract
The concentration and homeostasis of intracellular phosphate (Pi) are
crucial for sustaining cell metabolism and growth. During short-term Pi
starvation, intracellular Pi is maintained relatively constant at the
expense of vacuolar Pi. After the vacuolar stored Pi is exhausted, the
plant cells induce the synthesis of intracellular acid phosphatase
(APase) to recycle Pi from expendable organic phosphate (Po). In this
study, the expression, enzymatic activity and subcellular localization
of ACID PHOSPHATASE 1 (OsACP1) were determined. OsACP1 expression is
specifically induced in almost all cell types of leaves and roots under
Pi stress conditions. OsACP1 encodes an acid phosphatase with broad Po
substrates and localizes in the endoplasmic reticulum (ER) and Golgi
apparatus (GA). Phylogenic analysis demonstrates that OsACP1 has a
similar structure with human acid phosphatase PHOSPHO1. Overexpression
or mutation of OsACP1 affected Po degradation and utilization, which
further influenced plant growth and productivity under both
Pi-sufficient and Pi-deficient conditions. Moreover, overexpression of
OsACP1 significantly affected intracellular Pi homeostasis and Pi
starvation signalling. We concluded that OsACP1 is an active acid
phosphatase that regulates rice growth under Pi stress conditions by
recycling Pi from Po in the ER and GA.