State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Department of Plant and Microbial Biology, University of California-Berkeley, Berkeley, CA 94720, U.S.A.
Phytopathology. 2020 Jan;110(1):215-227. doi: 10.1094/PHYTO-06-19-0221-FI. Epub 2019 Dec 6.
(PSLV), (LRSV), and (BSMV) are members of the genus in the family . However, the biological properties and molecular genetics of PSLV have not been compared with other hordeiviruses. Here, we have constructed an infectious cDNA clone of the PSLV Canadian strain and provided evidence that PSLV differs from BSMV and LRSV. First, unlike the other two hordeiviruses that replicate in chloroplasts, PSLV induces dramatic structural changes in peroxisome during its infection in barley. The αa replication protein also localizes to peroxisomes, suggesting that PSLV replication occurs in peroxisomes. Second, PSLV encodes a γb protein that shares 19 to 23% identity with those of other hordeiviruses, and its activity as a viral suppressor of RNA (VSR) silencing is distinct from those of BSMV and LRSV. Substitution of the BSMV γb protein with that of PSLV or LRSV revealed a negative correlation between VSR activity and symptom severity of the recombinant BSMV derivatives. Intriguingly, the Ser-Lys-Leu (SKL) peroxisome-targeting signals differ among γb proteins of various hordeiviruses, including some BSMV strains. The presence of the C-terminal SKL motif in the γb protein impairs its silencing suppressor activity and influences symptoms. Finally, we developed a PSLV-based virus-induced gene silencing vector that induced strong and effective silencing phenotypes of endogenous genes in barley, wheat, and millet. Our results shed new light on hordeivirus pathogenesis and evolution, and provide an alternative tool for genomics studies of model hosts and economically important monocots.
（PSLV）、（LRSV）和（BSMV）是 科 的属成员。然而，PSLV 的生物学特性和分子遗传学尚未与其他霍多病毒进行比较。在这里，我们构建了 PSLV 加拿大株的传染性 cDNA 克隆，并提供了证据表明 PSLV 与 BSMV 和 LRSV 不同。首先，与其他两种在叶绿体中复制的霍多病毒不同，PSLV 在感染大麦时会导致过氧化物酶体发生剧烈的结构变化。αa 复制蛋白也定位于过氧化物酶体，表明 PSLV 复制发生在过氧化物酶体中。其次，PSLV 编码一种 γb 蛋白，与其他霍多病毒的同源性为 19%至 23%，其作为病毒 RNA（VSR）沉默抑制剂的活性与 BSMV 和 LRSV 不同。用 PSLV 或 LRSV 的 BSMV γb 蛋白取代发现，重组 BSMV 衍生物的 VSR 活性与症状严重程度之间存在负相关。有趣的是，各种霍多病毒（包括一些 BSMV 株）的 γb 蛋白中的 Ser-Lys-Leu（SKL）过氧化物酶体靶向信号不同。γb 蛋白中 C 末端 SKL 基序的存在会损害其沉默抑制剂活性并影响症状。最后，我们开发了一种基于 PSLV 的病毒诱导基因沉默载体，该载体可诱导大麦、小麦和谷子内源基因的强烈有效的沉默表型。我们的研究结果为霍多病毒的发病机制和进化提供了新的线索，并为模式宿主和重要经济单子叶植物的基因组学研究提供了一种替代工具。
