TEOSINTE BRANCHED1/CYCLOIDEA/PCF protein PeTCP4s positively regulate lateral bud development by activating PePIN2a expression in Phyllostachys edulis.

The development of lateral buds on the underground rhizome in bamboo is a major determinant of the yield of bamboo shoots. However, the regulating factors influencing this developmental process and the molecular mechanisms remain largely unknown. Here, we found that treatment with the Cytokinin significantly increased the lateral bud outgrowth of Moso bamboo (Phyllostachys edulis). A pair of plant-specific TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) genes, PeTCP4a and PeTCP4b, were identified in Moso bamboo. The expression of both PeTCP4 genes was promoted by Cytokinin and synchronized with the development of lateral buds. Overexpression of PeTCP4 genes exhibited increased rosette-leaf branches. PeTCP4s upregulated the expression of auxin efflux carrier PIN-FORMED (PIN2) gene and those genes involved in lateral organ such as KNAT2, KNAT6, STM and IAA3 in transgenic plants. Similar to PeTCP4 genes, the expression of PePIN2a in Moso bamboo was also promoted by Cytokinin. Subsequently, we found both PeTCP4 proteins directly bound to the PePIN2a gene and activated its expression. Our data suggested that PeTCP4s, induced by Cytokinin, promote lateral bud outgrowth by activating PePIN2a expression and upregulating the expression of those genes involved in lateral organ. This study may provide new insights into the mechanism of lateral bud development of bamboo.