Das Ayan, Sharma Namisha, Prasad Manoj
National Institute of Plant Genome Research, New Delhi, India.
Front Plant Sci. 2019 Jan 15;9:2008. doi: 10.3389/fpls.2018.02008. eCollection 2018.
Plant pathogens like virus, bacteria, and fungi incur a huge loss of global productivity. Targeting the dominant R gene resulted in the evolution of resistance in pathogens, which shifted plant pathologists' attention toward host susceptibility factors (or S genes). Herein, the application of sequence-specific nucleases (SSNs) for targeted genome editing are gaining more importance, which utilize the use of meganucleases (MN), zinc finger nucleases (ZFNs), transcription activator-like effector-based nucleases (TALEN) with the latest one namely clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). The first generation of genome editing technologies, due to their cumbersome nature, is becoming obsolete. Owing to its simple and inexpensive nature the use of CRISPR/Cas9 system has revolutionized targeted genome editing technology. CRISPR/Cas9 system has been exploited for developing resistance against virus, bacteria, and fungi. For resistance to DNA viruses (mainly single-stranded DNA viruses), different parts of the viral genome have been targeted transiently and by the development of transgenic plants. For RNA viruses, mainly the host susceptibility factors and very recently the viral RNA genome itself have been targeted. Fungal and bacterial resistance has been achieved mainly by targeting the host susceptibility genes through the development of transgenics. In spite of these successes CRISPR/Cas9 system suffers from off-targeting. This and other problems associated with this system are being tackled by the continuous discovery/evolution of new variants. Finally, the regulatory standpoint regarding CRISPR/Cas9 will determine the fate of using this versatile tool in developing pathogen resistance in crop plants.
病毒、细菌和真菌等植物病原体给全球生产力造成了巨大损失。针对显性R基因导致病原体产生抗性进化，这使得植物病理学家将注意力转向宿主感病因子（即S基因）。在此，用于靶向基因组编辑的序列特异性核酸酶（SSN）正变得越来越重要，其中包括巨核酸酶（MN）、锌指核酸酶（ZFN）、基于转录激活样效应因子的核酸酶（TALEN），最新的是成簇规律间隔短回文重复序列（CRISPR）/CRISPR相关蛋白9（Cas9）。第一代基因组编辑技术由于其操作繁琐，正逐渐过时。由于CRISPR/Cas9系统简单且成本低廉，它彻底改变了靶向基因组编辑技术。CRISPR/Cas9系统已被用于培育对病毒、细菌和真菌的抗性。对于DNA病毒（主要是单链DNA病毒）抗性，已通过瞬时靶向病毒基因组的不同部分以及培育转基因植物来实现。对于RNA病毒，主要靶向宿主感病因子，最近也开始靶向病毒RNA基因组本身。通过培育转基因植物靶向宿主感病基因，已实现了对真菌和细菌的抗性。尽管取得了这些成功，但CRISPR/Cas9系统仍存在脱靶问题。通过不断发现/进化新的变体，正在解决该系统的这一问题及其他相关问题。最后，关于CRISPR/Cas9的监管立场将决定在培育作物对病原体的抗性中使用这一多功能工具的命运。
