Perspective: Challenging battles of plants with phloem-feeding insects and prokaryotic pathogens (PNAS)

Much of our understanding of plant defense response is built upon the responses that occur in leaves. Many pathogens colonize the phloem system, which is both nutrient-rich and provides an easy conduit for spreading through systemically through the plant body. These phloem-inhabiting prokaryotic pathogens are introduced and spread through phloem-feeding insects.  Jiang et al. describe the challenges in studying these pathogens, which can cause serious diseases including citrus greening disease (aka “huanglongbin” or HLB). Phloem-resident prokaryotic pathogens include phytoplasmas and spiroplasmas, which are notable both for having a reduced genome and being difficult (or impossible) to culture in vitro, contributing to the challenges of studying them. (Summary by Mary Williams) Proc. Natl. Acad. Sci. USA 10.1073/pnas.1915396116. (This PNAS perspective is contributed by Sheng Yang He, who is also featured in a QnA