Abstract
The mediator complex is an essential link between transcription factors and RNA polymerase II, and mainly functions in the transduction of diverse signals to genes involved in different pathways. Limited information is available on the role of soybean mediator subunits in growth and development, and their participation in defense response regulation. Here, we performed genome-wide identification of the 95 soybean mediator subunits, which were unevenly localized on the 20 chromosomes and only segmental duplication events were detected. We focused on GmMED16-1, which is highly expressed in the roots, for further functional analysis. Transcription of GmMED16-1 was induced in response to Phytophthora sojae infection. Agrobacterium rhizogenes mediated soybean hairy root transformation was performed for the silencing of the GmMED16-1 gene. Silencing of GmMED16-1 led to an enhanced susceptibility phenotype and increased accumulation of P. sojae biomass in hairy roots of transformants. The transcript levels of NPR1, PR1a, and PR5 in the salicylic acid defense pathway in roots of GmMED16-1-silenced transformants were lower than those of empty-vector transformants. The results provide evidence that GmMED16-1 may participate in the soybean–P. sojae interaction via a salicylic acid-dependent process.
Highlights
The mediator complex, a component of the RNA polymerase II transcription system, is a crucial regulatory element of the transcriptional machinery and is likely to facilitate a variety of functional interactions
We revealed the roles of GmMED16-1 in soybean–P. sojae interaction
95 mediator complex subunits were identified in soybean based on the domains of mediator proteins predicted with the Pfam database
Summary
The mediator complex, a component of the RNA polymerase II transcription system, is a crucial regulatory element of the transcriptional machinery and is likely to facilitate a variety of functional interactions. Two tail subunits of the mediator complex, MED14 and MED15, have been reported to be critical regulators of the salicylic acid (SA) response as well as the systemic acquired resistance (SAR) signaling pathway, which is similar to NPR1 [12,13]. An additional ERF transcription factor, GmERF113, is reported to play a crucial role in the defense of soybean against P. sojae infection. GmBTB/POZ, a novel BTB/POZ domain-containing nuclear protein, plays a positive role in P. sojae resistance and the defense response in soybean via a process that might be dependent on SA [31]. The former name for Mediator 16 (MED16), a tail subunit in the mediator complex, is Sensitive to Freezing 6 (SFR6). The results suggest that GmMED16-1 positively regulates resistance to P. sojae infection in soybean
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