Genetic dissection of tomato bushy stunt virus p19-protein-mediated host-dependent symptom induction and systemic invasion
Genetic dissection of tomato bushy stunt virus p19-protein-mediated host-dependent symptom induction and systemic invasion
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DOI：
10.1006/viro.1999.0071
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发表时间：
2000-01-05
期刊：
影响因子：
3.7
通讯作者：
Scholthof, HB
中科院分区：
文献类型：
--
作者：
Chu, M;Desvoyes, B;Scholthof, HB
番茄丛突病毒（TBSV）的正义单链RNA编码一个19 kda的蛋白，该蛋白是从完全嵌套在细胞间运动基因（p22）内的3'近端开放阅读框（p19）翻译过来的。细胞质p19蛋白的表达可引起本烟和克利夫兰烟草的系统性致死衰竭，或引起耐药烟草的局部坏死。在菠菜中，p19蛋白是有效的系统入侵所需的高丰度蛋白质。本研究旨在确定这些看似不同的寄主依赖性生物活性是否由172个氨基酸p19蛋白上相同或单独的区域控制。为此，预计暴露在多肽表面的带电氨基酸的密码子可能用于宿主特异性相互作用，从而成为诱变的目标。共产生了12个突变体，这些突变体在复制和细胞间运动方面没有缺陷，在n末端或羧基70个氨基酸内的氨基酸替代未能对植物产生明显的生物学效应。然而，分散在n端第43和85位的突变阻止了benthamiana和n.l clevelandii发生系统性致死坏死。除了一个例外，相同的突变在烟草上引起的大多是褪绿而不是坏死的局部病变。在中心区域的突变中，在72位或75-78位用Gly取代Arg，削弱了TBSV系统入侵菠菜植株的能力。然而，在72位用Ala代替Gly对菠菜的全身传播影响很小，这表明可能影响蛋白质结构效应。这意味着p19蛋白n端部分的区域以宿主依赖的方式介导相互作用，并且通过氨基酸的直接作用或通过维持结构完整性，所有活性都需要一个中心区域。(C) 2000年学术出版社。
The plus-sense single-stranded RNA of tomato bushy stunt virus (TBSV) encodes a 19-kDa protein, which is translated from a 3' proximal open reading frame (p19) that is entirely nested within the cell-to-cell movement gene (p22). Expression of the cytosolic p19-protein induces either a systemic lethal collapse in Nicotiana benthamiana and N. clevelandii, or necrotic local lesions on resistant N. tabacum. In spinach, the p19-protein is required at high abundance for efficient systemic invasion. This study aimed to determine whether these seemingly different host-dependent biological activities are governed by the same or separate regions on the 172 amino acid p19-protein. For this purpose, codons for charged amino acids predicted to be exposed on the surface of the polypeptide and presumably available for host-specific interactions, were targeted for mutagenesis. A total of 12 mutants were generated, which had no deficiencies in replication or cell-to-cell movement, and substitution of amino acids at the extreme N-terminal end or within the carboxyl 70 amino acids failed to cause a noticeable biological effect on plants. However, mutations dispersed between positions 43 and 85 on the N-terminal half prevented the onset of a systemic lethal necrosis on N. benthamiana and N. clevelandii. With one exception, the same mutants elicited mostly chlorotic, rather than necrotic, local lesions on N. tabacum. Mutations in the central region, which substituted Arg with Gly at positions 72 or 75-78, impaired the ability of TBSV to systemically invade spinach plants. However, substitution with Ala instead of Gly at position 72 had minimal effects on systemic spread in spinach, suggesting the possible influence of protein structure effects. The implications are that regions on the N-terminal portion of the p19-protein mediate interactions in a host-dependent manner and that a central region is required for all activities either by a direct effect of the amino acids or through maintenance of structural integrity. (C) 2000 academic Press.