In eukaryotic cells, communication among different cellular compartments and between cells and their environment depends on vesicle trafficking. In mammalian cells, BLOC-1 (biogenesis of lysosome-related organelles complex 1; an eight-subunit protein complex) is involved in endosome-to-lysosome transport. Now, Wei Li, Klaus Palme and colleagues (p. 3727) provide the first evidence for the involvement of a BLOC-1 endosomal transport complex in vesicle trafficking in plants, which is a poorly characterised process. The authors identify Arabidopsis homologues of the BLOS1 and BLOS2 subunits of mammalian BLOC-1, and show that both subunits interact with the recently described plant nexin SNX1 on sorting endosomes. RNAi downregulation of BLOS1, they report, leads to the formation of longer than normal primary and lateral roots. Consistent with this finding, the levels of the auxin efflux carriers PIN1 and PIN2, which regulate the intercellular flow of plant phytohormones, are increased in BLOS1 RNAi lines. The authors suggest, therefore, that a putative BLOC-1 complex, through direct interaction with SNX1, regulates PIN1 and PIN2 homeostasis in Arabidopsis by mediating their transport to degradative vacuoles, thereby modulating root growth.
- © 2010.