MsPG1 alleviated aluminum-induced inhibition of root growth by decreasing aluminum accumulation and increasing porosity and extensibility of cell walls in alfalfa (Medicago sativa)

Pectins are abundant in the primary cell walls and involve in regulating intercellular adhesion. MsPG1gene was cloned from alfalfa and its function of Al tolerance was tested in vivo and vitro. Results showed that the expression of MsPG1 was increased by Al, and the MsPG1 was localized in the plasma membrane of epidermal cells in root apexes. Overexpression of MsPG1 in hairy roots of alfalfa increased root growth in the present of Al, which was attributed to the decreased Al accumulations in pectins, hemicellulose 1 (HC1), cell walls and root apexes conferred by the decreased content of HC1 and ratios of negatively charged functional groups ( - OH and - COOH) in cell wall. The decreased Al accumulations in pectins and cell walls were also observed in incubation MsPG1 with pectins and cell walls in vitro. TEM and FESEM assays showed that overexpression of MsPG1 protected the cell microstructure of root apexes, and increased the porosity and pore size of porous lattice-like structure of cell wall in the present of Al. These results indicated that MsPG1 could increase Al tolerance of alfalfa via decreasing Al accumulation in cell wall and increasing the porosity and extensibility of cell wall under excess Al stress.