Plant viruses cause various disease in crops and are responsible for huge economic losses. Understanding their mode of infection and spread is crucial for developing control strategies. Genome packaging is an important step in the process of viral maturation. Three systems of viral genome packaging are known till date. The type I packaging system, found in most of the small plant viruses, involves co-condensation of nucleic acid with viral capsid proteins (CPs) leading to the assembly of virion particles without utilizing ATP. The type II and III packaging systems, present in phages and nucleo-cytoplasmic large DNA viruses, exhibit genome translocation inside the prohead by utilizing ATP. Discovery of the ATPase fold in the CPs of many small plant viruses and the requirement of other ATPases during genome encapsidation have changed the perception about genome packaging in the type I system. Based on recent studies, it seems that the genome packaging mechanisms of plant viruses such as potexvirus have nothing in common with those of other well-characterized passive, energy-independent type I systems. Moreover, these studies have suggested that in these plant viruses, the genome encapsidation process is more intricately coupled with energy utilization than in other systems. In this comprehensive review, we present a novel, expanded sub-classification system for the type I system on the basis of ATP employed.

植物病毒在农作物中引起各种疾病，并造成巨大的经济损失。了解它们的感染和传播方式对于制定控制策略至关重要。基因组包装是病毒成熟过程中的重要步骤。迄今为止，已知三种病毒基因组包装系统。大多数小型植物病毒中都存在I型包装系统，该系统涉及核酸与病毒衣壳蛋白（CP）的共缩合，导致病毒体颗粒的组装而不利用ATP。存在于噬菌体和核质大DNA病毒中的II型和III型包装系统通过利用ATP在前额体内表现出基因组易位。许多小植物病毒的CP中ATPase折叠的发现以及基因组壳体化过程中对其他ATPase的需求已经改变了人们对I型系统中基因组包装的认识。根据最近的研究，似乎植物病毒（如potexvirus）的基因组包装机制与其他特征鲜明的被动式，独立于能量的I型系统没有任何共同点。此外，这些研究表明，与其他系统相比，在这些植物病毒中，基因组的衣壳化过程与能量利用更加复杂。在这项全面的综述中，我们将基于所采用的ATP为I型系统提供一种新颖的扩展子分类系统。似乎植物病毒（如potexvirus）的基因组包装机制与其他特征鲜明的被动，与能量无关的I型系统没有任何共同点。此外，这些研究表明，与其他系统相比，在这些植物病毒中，基因组的衣壳化过程与能量利用更加复杂。在这项全面的综述中，我们将基于所采用的ATP为I型系统提供一种新颖的扩展子分类系统。似乎植物病毒（如potexvirus）的基因组包装机制与其他特征鲜明的被动，与能量无关的I型系统没有任何共同点。此外，这些研究表明，与其他系统相比，在这些植物病毒中，基因组的衣壳化过程与能量利用更加复杂。在这项全面的综述中，我们将基于所采用的ATP为I型系统提供一种新颖的扩展子分类系统。