Plant Pathology Laboratory, Faculty of Agriculture, Iwate University, 18-8, Ueda 3-chome, Morioka, 020-8550, Japan.
Graduate School of Life Sciences, Tohoku University, 1-1, Katahira 2-chome, Aoba-ku, Sendai, 980-8577, Japan.
Arch Virol. 2023 Apr 12;168(5):138. doi: 10.1007/s00705-023-05767-w.
Raspberry bushy dwarf virus (RBDV) is transmitted through seed in infected red raspberry plants after pollination with pollen grains from healthy red raspberry plants. Here, we show that RBDV is not transmitted through seeds in infected Nicotiana benthamiana (Nb) plants after pollination with virus-free Nb pollen grains. Chromogenic in situ hybridization revealed that the virus invades the shoot apical meristem and the ovule, including the embryo sac, of RBDV-infected Nb plants; however, in seeds that developed from infected embryo sacs after fertilization by virus-free sperm cells, RBDV was absent in the embryos and present in the endosperms. When we analyzed seed transmission of RBDV in Nb mutants with mutations in dicer-like enzyme 2 and 4 (NbDCL2&4) or RNA-dependent RNA polymerase 6 (NbRDR6), RBDV was not present in the offspring from seeds with embryos and endosperms that did not express NbDCL2&4 or NbRDR6. These results suggest that seed transmission of RBDV is prevented by evasion of infection by the embryo and that RNA silencing is not essential for preventing seed transmission of RBDV in Nb plants.
树莓丛枝矮化病毒（RBDV）通过授粉花粉粒从健康的红树莓植物授粉后在感染的红树莓植物种子中传播。在这里，我们表明，RBDV 没有通过授粉授粉花粉粒的病毒在感染的 Nicotiana benthamiana（Nb）植物的种子中传播。显色原位杂交显示病毒侵入芽顶端分生组织和胚珠，包括胚囊，RBDV 感染的 Nb 植物; 然而，在由无病毒精子受精后从受感染的胚囊发育而来的种子中，胚胎中不存在 RBDV，而在胚乳中存在。当我们分析具有二肽酶样酶 2 和 4（NbDCL2＆4）或 RNA 依赖性 RNA 聚合酶 6（NbRDR6）突变的 Nb 突变体中 RBDV 的种子传播时，来自未表达 NbDCL2＆4 或 NbRDR6 的种子的后代中不存在 RBDV。这些结果表明，胚胎对感染的逃避阻止了 RBDV 的种子传播，并且 RNA 沉默对于防止 Nb 植物中 RBDV 的种子传播不是必需的。
