Open AccessAnalysis of T omato spotted wilt virus NSs protein indicates the importance of the N ‐terminal domain for avirulence and RNA silencing suppression
Author(s) -
Ronde Dryas,
Pasquier Adrien,
Ying Su,
Butterbach Patrick,
Lohuis Dick,
Kormelink Richard
Publication year - 2014
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1111/mpp.12082
Subject(s) - biology , mutant , rna interference , rna silencing , amino acid , gene silencing , rna , gene , genetics
Summary Recently, T omato spotted wilt virus ( TSWV ) nonstructural protein NSs has been identified unambiguously as an avirulence ( A vr) determinant for T omato spotted wilt ( T sw )‐based resistance. The observation that NSs from two natural resistance‐breaking isolates had lost RNA silencing suppressor ( RSS ) activity and Avr suggested a link between the two functions. To test this, a large set of NSs mutants was generated by alanine substitutions in NSs from resistance‐inducing wild‐type strains ( NSs RI ), amino acid reversions in NSs from resistance‐breaking strains ( NSs RB ), domain deletions and swapping. Testing these mutants for their ability to suppress green fluorescent protein ( GFP ) silencing and to trigger a T sw ‐mediated hypersensitive response ( HR ) revealed that the two functions can be separated. Changes in the N ‐terminal domain were found to be detrimental for both activities and indicated the importance of this domain, additionally supported by domain swapping between NSs RI and NSs RB . Swapping domains between the closely related T ospovirus Groundnut ringspot virus ( GRSV ) NSs and TSWV NSs RI showed that A vr functionality could not simply be transferred between species. Although deletion of the C ‐terminal domain rendered NSs completely dysfunctional, only a few single‐amino‐acid mutations in the C ‐terminus affected both functions. Mutation of a GW / WG motif (position 17/18) rendered NSs completely dysfunctional for RSS and A vr activity, and indicated a putative interaction between NSs and A rgonaute 1 ( AGO1 ), and its importance in TSWV virulence and viral counter defence against RNA interference.