CONTRASTING PATTERNS IN THE SPREAD OF 2 SEED-BORNE VIRUSES IN PEA EMBRYOS

The temporal and spatial patterns of pea seed-borne mosaic potyvirus ( PSbMV) and pea early browning tobravirus (PEBV) accumulation in pea em bryos were analyzed using in-situ hybridization and immunohistochemist ry. For PSbMV, which infects embryos after fertilization, the distribu tion changed as the embryo developed and some tissues remained free of virus infection. In contrast, embryos were uniformly infected with PE BV from the earliest stages of embryo development, and PEBV was detect ed in the egg cell and pollen grains, indicative of gametic transmissi on into the embryo. These observations suggest that gametically transm itted viruses may be appropriate as potential vectors for the ectopic and uniform expression of novel genes in embryonic tissues. Functional complementarity in the two processes of embryo invasion was tested fo llowing co-inoculation with PSbMV and PEBV. Instead of complementation , interference in PSbMV seed transmission by PEBV was observed; PEBV s eed transmission remained unaffected by PSbMV.