An autophagy-related kinase is essential for Phaseolus vulgaris symbiosis with both Rhizobium and arbuscular endomycorrhizal fungi

MS. GEORGINA ESTRADA-NAVARRETE, MR. NEFTALY CRUZ-MIRELES, RAMIRO LASCANO , MRS. XOCHITL ALVARADO-AFFANTRANGER, MS. ALEJANDRA HERNÀNDEZ, AARON BARRAZA MR. JUAN ELIAS OLIVARES, DR. MANOJ KUMAR ARTHIKALA, LUIS CARDENAS, CARMEN QUINTO FEDERICO SANCHEZ

PLANT CELL

AMER SOC PLANT BIOLOGISTS

Lugar: Rockville; Año: 2016

1040-4651

Eukaryotes contain three types of lipid kinases belonging to the phosphatidylinositol 3-kinase (PI3K) family. In plants and Saccharomyces, only PI3K class III family members have been found. These enzymes regulate senescence, the innate immune response, autophagy and intracellular trafficking. Here, we report that RNAi-mediated down-regulation of P. vulgaris PvPI3K, severely impaired symbiosis in composite common bean plants with endosymbionts such as Rhizobium tropici and Rhizophagus irregularis. When PvPI3K was downregulated, a marked decrease in root hair growth and curling was observed. Additionally, infection thread growth, root-nodule number, and symbiosome formation in root nodule cells were also severely affected. Interestingly, root colonization by AM fungi, the formation of arbuscules was also abrogated in PI3K loss-of-function plants. Furthermore, the transcript accumulation of genes encoding proteins known to interact with PI3K to form protein complexes involved in autophagy was drastically reduced in these transgenic roots. Expression of one of these genes, Beclin1 / Atg6, was also knocked-down by RNAi, resulting in a similar impaired-symbiosis phenotype as that observed in PvPI3K down-regulated transgenic roots. Our findings show for the first time that an autophagy-related process is crucial for the mutualistic interactions of P. vulgaris with beneficial microorganisms.