**Weiwei Wu, Shengnan Zhu, Qianqian Chen, Yan Lin, Jiang Tian and Cuiyue Liang \***

Root Biology Center, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China; weiweiwu2016@163.com (W.W.); shnzhu@163.com (S.Z.); qian2016200202@163.com (Q.C.); anlynlin@126.com (Y.L.); jtian@scau.edu.cn (J.T.) **\*** Correspondence: liangcy@scau.edu.cn; Tel.: +86-20-8528-0156; Fax: +86-20-8528-1829

Received: 2 August 2019; Accepted: 14 October 2019; Published: 23 October 2019

**Abstract:** Phosphorus is one of the mineral nutrient elements essential for plant growth and development. Low phosphate (Pi) availability in soils adversely affects crop production. To cope with low P stress, remodeling of root morphology and architecture is generally observed in plants, which must be accompanied by root cell wall modifications. It has been documented that cell wall proteins (CWPs) play critical roles in shaping cell walls, transmitting signals, and protecting cells against environmental stresses. However, understanding of the functions of CWPs involved in plant adaptation to P deficiency remains fragmentary. The aim of this review was to summarize advances in identification and functional characterization of CWPs in responses to P deficiency, and to highlight the critical roles of CWPs in mediating root growth, P reutilization, and mobilization in plants.

**Keywords:** cell wall protein; phosphate starvation; Pi mobilization; roots
