Changes in the Common Bean Transcriptome in Response to Secreted and Surface Signal Molecules of Rhizobium etli

VIRGINIA DALLA VIA, CANDELA NARDUZZI, ORLANDO MARIO AGUILAR, MARÍA EUGENIA ZANETTI, AND FLAVIO ANTONIO BLANCO

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Lugar: Rockville; Año: 2015 vol. 169 p. 1356 - 1370

0032-0889

Establishment of nitrogen-fixing symbiosis requires the recognition of rhizobial molecules to initiate the development of nodules.Using transcriptional profiling of roots inoculated with mutant strains defective in the synthesis of Nod Factor (NF),exopolysaccharide (EPS), or lipopolysaccharide (LPS), we identified 2,606 genes from common bean (Phaseolus vulgaris) thatare differentially regulated at early stages of its interaction with Rhizobium etli. Many transcription factors from different familiesare modulated by NF, EPS, and LPS in different combinations, suggesting that the plant response depends on the integration ofmultiple signals. Some receptors identified as differentially expressed constitute excellent candidates to participate in signalperception of molecules derived from the bacteria. Several components of the ethylene signal response, a hormone that plays anegative role during early stages of the process, were down-regulated by NF and LPS. In addition, genes encoding proteinsinvolved in small RNA-mediated gene regulation were regulated by these signal molecules, such as Argonaute7, a specificcomponent of the trans-acting short interfering RNA3 pathway, an RNA-dependent RNA polymerase, and an XH/XP domaincontainingprotein, which is part of the RNA-directed DNA methylation. Interestingly, a number of genes encoding componentsof the circadian central oscillator were down-regulated by NF and LPS, suggesting that a root circadian clock is adjusted at earlystages of symbiosis. Our results reveal a complex interaction of the responses triggered by NF, LPS, and EPS that integratesinformation of the signals present in the surface or secreted by rhizobia.