Recent research shows that significant energy saving can be achieved in wireless sensor networks (WSNs) by introducing mobile collector (MC). One obvious bottleneck of such approach is the large data collection latency due to low mobile speed of MC. In this paper, we propose an efficient rendezvous based mobile data gathering protocol for WSNs, in which the aggregated data will be relayed to Rendezvous Node (RN) within bounded hop d. The algorithm design in the protocol jointly considers MC tour and data routing routes in aggregation trees. The effectiveness of the approach is validated through both theoretical analysis and extensive simulations.