A Model for Seed Transmission of a Plant Virus: Genetic and Structural Analyses of Pea Embryo Invasion by Pea Seed-Borne Mosaic Virus.

Abstract

Pea seed-borne mosaic virus (PSbMV), a seed-transmitted virus in pea and other legumes, invades pea embryos early in development. This process is controlled by maternal genes and, in a cultivar that shows no seed transmission, is prevented through the action of multiple host genes segregating as quantitative trait loci. These genes control the ability of PSbMV to spread into and/or multiply in the nonvascular testa tissues, thereby preventing the virus from crossing the boundary between the maternal and progeny tissues. lmmunocytochemical and in situ hybridization studies suggested that the virus uses the embryonic suspensor as the route for the direct invasion of the embryo. The programmed degeneration of the suspensor during embryo development may provide a transient window for embryo invasion by the virus and could explain the inverse relationship between the age of the mother plant for virus infection and the extent of virus seed transmission.

Multiple viral determinants affect seed transmission of pea seedborne mosaic virus in Pisum sativum

“…The observation that seed transmission is affected by multiple determinants in the viral genome agrees well with the results of Wang & Maule (1994) who demonstrated that resistance to seed transmission in P. sativum involves several nuclear genes. This suggests that several virus-host factor interactions determine the spread and accumulation of PSbMV in the maternal testa tissue.…”

“…The region of HCpro contained in HCpro N affects aphid transmission, replication (Atreya et al, 1992) and long-distance movement (Cronin et al, 1995). Wang & Maule (1994) demonstrated that the suspensor can act as a channel for transmission of PSbMV to the embryo proper. A prerequisite for embryo infection is, therefore, that virus reaches the micropylar region of the testa before disintegration of the suspensor.…”

“…In Hordeum vulgare cultivar Modjo, resistance was reported to be conditioned by a single recessive gene (Carroll et al, 1979), whereas resistance to seed transmission of pea seedborne mosaic potyvirus (PSbMV) in Pisum sativum is Author for correspondence: I. E. Johansen. Fax +45 45 93 22 13. e-mail e.johansen@dips-lyngby.dk inherited as a quantitative character controlled by the action of multiple maternal genes (Wang & Maule, 1994). In a single host cultivar, different virus isolates are seed-transmitted to different degrees.…”

Similarities in Seed and Aphid Transmission Among Soybean mosaic virus Isolates

“…While differences in seed transmission of Pea seed borne mosaic virus (PSbMV) were associated with the inability of poorly seed-transmitted virus isolates to invade embryos (42), Bowers and Goodman (6) reported that cultivar-specific differences in seed transmission of a severe isolate of SMV were related to differences in the abilities of SMV strains to remain infectious within maturing embryos. Seed-transmissible strains of PSbMV were shown to enter developing embryos through a transient symplastic pathway that connects the base of the suspensor to the developing embryo (37).…”

Evaluation of Seed Transmissibility of Soybean Vein Necrosis-Associated Virus in Two Soybean Cultivars Grown Under Field Conditions

“…It should be noted that there are two distinct routes leading to seed transmissibility of a particular virus in a particular plant host; infected embryo from an infected mother plant or fertilization of an ovule of a virus free mother plant with infected pollen originating from another infected plant [15,16,26,33]. Regardless of the route, a virus must be capable of crossing the boundary between the non-productive and productive tissues in an infected plant in order for seed transmission to occur [26].…”