OsAPL controls long-distance transport system-Trancriptome sequencing

Plant growth depends mainly on the photoassimilates synthesized in leaves and mineral nutrient uptake through roots. Photosynthates and nutrients allocation from source organs to specific sink organs in plants starts with the phloem loading in collection phloem, transports along the path through transport phloem and ends up with the phloem unloading in release phloem6 and occurs either through symplast (moving via plasmodesmata) or apoplast (moving across membranes via transporters)1-1. Especially in sink organs, typically developing seeds, the arrangement of phloem unloading appear to be apoplastic, as there are no symplastic connections between glumes and the embryo tissue. The apoplastic transmembrane allocation processes relies on the efficiency and number of primary and secondary transporters 126. Here we show that the orthologue of AtAPL (ALTERED PHLOEM DEVELOPMENT), OsAPL, controls long-distance transport system in rice. Overexpression of OsAPL leads to an increase in plant height at early developmental stage, grain size and yield at heading stage, while knockdown of which leads to the opposite phenotypes. OsAPL expressed highly in leaf blade and glume, especially in mesophyll cells. We also show that OsAPL acts as the transcription activator of OsATP6, which encodes a subunit of plasma membrane (PM) H+-ATPase (primary transporter) and OsAPL seriously affects the expression of a series of genes encoding H+-coupled secondary active transporters. The regulation module of OsAPL on OsATP6 suggests its involvement in photosynthates transport, sink-source communication, and trafficking of secondary active transporters to sieve elements. OsAPL regulating rice plant height and yield will provide important theoretical guidance for future rice breeding and genetic engineering operations.