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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #332128
Title: The coat protein and NIa protease of two potyviridae family members independently confer superinfection exclusion

Author
item Tatineni, Satyanarayana - Ts
item FRENCH, ROY - Retired ARS Employee

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2016
Publication Date: 11/15/2016
Publication URL: http://handle.nal.usda.gov/10113/63319
Citation: Tatineni, S., French, R. 2016. The coat protein and NIa protease of two Potyviridae family members independently confer superinfection exclusion. Journal of Virology. 90(23):10886-10905.

Interpretive Summary: Superinfection exclusion or cross-protection occurs when infection of a plant by one virus prevents infection by additional closely related viruses. Superinfection exclusion has been reported in diverse virus species, but the key components and mechanisms involved are poorly understood. In this study, the role of virus-encoded proteins in superinfection exclusion activity of Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) was determined. WSMV and TriMV encode two independently functioning effectors of superinfection exclusion at the protein but not the RNA level. The coat protein and nuclear inclusion protein a protease gene of WSMV and coat protein of TriMV are strong effectors of superinfection exclusion, while the TriMV-encoded nuclear inclusion protein a protease is a weak effector. Identifying virus-encoded superinfection exclusion effectors could potentially facilitate the development of virus-resistant transgenic plants by expressing superinfection exclusion effector genes. This method would eliminate the use of live mild virus strains in cross protection, thus preventing the risk of accidental escape of cross protecting viruses and unintended multi-viral synergistic effects.

Technical Abstract: Superinfection exclusion (SIE) is an antagonistic virus-virus interaction whereby initial infection by one virus prevents subsequent infection by closely related viruses. Although SIE has been described in diverse viruses infecting plants, humans, and animals, its mechanisms, including involvement of specific viral determinants, are just beginning to be elucidated. In this study, SIE determinants encoded by two economically important wheat viruses, Wheat streak mosaic virus (WSMV; genus Tritimovirus, family Potyviridae) and Triticum mosaic virus (TriMV; genus Poacevirus, family Potyviridae), were identified in gain-of-function experiments that used heterologous viruses to express individual virus-encoded proteins in wheat. Wheat plants infected with TriMV expressing WSMV P1, HC-Pro, P3, 6K1, CI, 6K2, NIa-VPg, or NIb cistrons permitted efficient superinfection by WSMV expressing green fluorescent protein (WSMV-GFP). In contrast, wheat infected with TriMV expressing WSMV NIa-Pro or coat protein (CP) substantially excluded superinfection by WSMV-GFP, suggesting that both of these cistrons are SIE effectors encoded by WSMV. Importantly, SIE is due to functional WSMV NIa-Pro or CP rather than their encoding RNAs, as altering the coded protein products by minimally changing RNA sequences led to abolishment of SIE. Deletion mutagenesis further revealed that elicitation of SIE by NIa-Pro requires the entire protein while CP requires only a 200-amino-acid (aa) middle fragment (aa 101 to 300) of the 349 aa. Strikingly, reciprocal experiments with WSMV-mediated expression of TriMV proteins showed that TriMV CP, and TriMV NIa-Pro to a lesser extent, likewise excluded superinfection by TriMV-GFP. Collectively, these data demonstrate that WSMV- and TriMV-encoded CP and NIa-Pro proteins are effectors of SIE and that these two proteins trigger SIE independently of each other.