Departamento de Virologia, Instituto de Microbiologia, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, 21941-590, Brazil.
Departamento de Biotecnologia, Escola de Engenharia de Lorena/Universidade de São Paulo (EEL/USP), Lorena, SP, 12602-810, Brazil.
BMC Plant Biol. 2019 Nov 15;19(1):503. doi: 10.1186/s12870-019-2112-4.
Dicer-like proteins (DCLs) are essential players in RNA-silencing mechanisms, acting in gene regulation via miRNAs and in antiviral protection in plants and have also been associated to other biotic and abiotic stresses. To the best of our knowledge, despite being identified in some crops, cotton DCLs haven't been characterized until now. In this work, we characterized the DCLs of three cotton species and analyzed their expression profiles during biotic stress.
As main results, 11 DCLs in the allotetraploid cotton Gossypium hirsutum, 7 and 6 in the diploid G. arboreum and G. raimondii, were identified, respectively. Among some DCLs duplications observed in these genomes, the presence of an extra DCL3 in the three cotton species were detected, which haven't been found in others eudicots. All the DCL types identified by in silico analysis in the allotetraploid cotton genome were able to generate transcripts, as observed by gene expression analysis in distinct tissues. Based on the importance of DCLs for plant defense against virus, responses of cotton DCLs to virus infection and/or herbivore attack using two commercial cotton cultivars (cv.), one susceptible (FM966) and another resistant (DO) to polerovirus CLRDV infection, were analyzed. Both cvs. Responded differently to virus infection. At the inoculation site, the resistant cv. showed strong induction of DCL2a and b, while the susceptible cv. showed a down-regulation of these genes, wherever DCL4 expression was highly induced. A time course of DCL expression in aerial parts far from inoculation site along infection showed that DCL2b and DCL4 were repressed 24 h after infection in the susceptible cotton. As CLRDV is aphid-transmitted, herbivore attack was also checked. Opposite expression pattern of DCL2a and b and DCL4 was observed for R and S cottons, showing that aphid feeding alone may induce DCL modulation.
Almost all the DCLs of the allotetraploide G. hirsutum cotton were found in their relative diploids. Duplications of DCL2 and DCL3 were found in the three species. All four classes of DCL responded to aphid attack and virus infection in G. hirsutum. DCLs initial responses against the virus itself and/or herbivore attack may be contributing towards virus resistance.
Dicer-like 蛋白（DCLs）是 RNA 沉默机制中的重要参与者，通过 miRNA 参与基因调控，并在植物的抗病毒保护中发挥作用，也与其他生物和非生物胁迫有关。据我们所知，尽管在一些作物中已经鉴定出了 DCLs，但直到现在棉花的 DCLs 还没有被描述过。在这项工作中，我们对三种棉花物种的 DCLs 进行了特征描述，并分析了它们在生物胁迫下的表达谱。
作为主要结果，在四倍体棉花 Gossypium hirsutum 中鉴定出 11 个 DCLs，在二倍体 G. arboreum 和 G. raimondii 中分别鉴定出 7 个和 6 个。在这些基因组中观察到的一些 DCL 重复中，在这三种棉花中都检测到了一个额外的 DCL3，而在其他真双子叶植物中并没有发现。在四倍体棉花基因组中通过计算机分析鉴定的所有 DCL 类型都能够产生转录物，这在不同组织的基因表达分析中得到了观察。鉴于 DCLs 对植物抗病毒的重要性，我们分析了两种商业棉花品种（cv.）对病毒感染和/或草食性动物攻击的反应，一个是易感（FM966），另一个是抗（DO）对 polerovirus CLRDV 感染。这两种品种的反应不同。在接种部位，抗性品种表现出强烈的 DCL2a 和 b 的诱导，而敏感品种表现出这些基因的下调，而 DCL4 的表达则被高度诱导。在感染过程中，远离接种部位的地上部分的 DCL 表达的时间进程表明，在易感棉花中，DCL2b 和 DCL4 在感染后 24 小时被抑制。由于 CLRDV 是通过蚜虫传播的，因此还检查了草食性动物的攻击。在 R 和 S 棉花中观察到 DCL2a 和 b 以及 DCL4 的表达模式相反，表明单独的蚜虫取食可能诱导 DCL 调节。
四倍体 G. hirsutum 棉花的几乎所有 DCLs 都在它们的相对二倍体中被发现。在三个物种中都发现了 DCL2 和 DCL3 的重复。DCL 的所有四个类群都对蚜虫的攻击和病毒的感染作出反应。DCLs 对病毒本身和/或草食性动物攻击的最初反应可能有助于病毒的抗性。
