Effects of polygalacturonase overexpression on pectin distribution in the elongation zones of roots under aluminium stress

Aluminium (Al) toxicity has long been known to damage plant cells and inhibits the growth of plants. The roots of many plant species contain large amounts of pectin and it contributes to the formation of the rhizosphere. Pectin degradation enzyme gene overexpressor rice allowed the authors to piece together how rice plant cells and cell wall pectin respond to Al. The authors found that pectin accumulation in cell walls in the root elongation zone may play a role in protecting rice plants from the Al-induced inhibition of root elongation by regulating pectin distribution. The roots of many plant species contain large amounts of pectin and it contributes to the formation of the rhizosphere. In the present study, the relationship between the root-tip pectin content and aluminium (Al) tolerance in wild-type (WT) and demethylesterified pectin degradation enzyme gene overexpressor (OsPG2-FOX) rice lines was compared. OsPG2-FOX rice showed reduced pectin content in roots, even under control conditions; Al treatment reduced root elongation and the pectin content in the root elongation zone. Wild-type rice showed more pectin accumulation in the root elongation zone after Al treatment. Relative to WT rice, OsPG2-FOX rice showed more Al accumulation in the root elongation zone. These results indicate that the amount of pectin influences Al tolerance and that the distribution of pectin in the root elongation zone inhibits Al accumulation in rice roots. Pectin accumulation in cell walls in the root elongation zone may play a role in protecting rice plants from the Al-induced inhibition of root elongation by regulating pectin distribution.