Contributed by Sheng Yang He, October 14, 2019 (sent for review September 5, 2019; reviewed by Ian T. Baldwin and Gitta Coaker)
Piercing-sucking insects and phloem-inhabiting prokaryotic pathogens contribute to some of the world’s most disastrous crop losses, including those caused by the brown plant hopper in rice or citrus greening in citrus. For historic and technical reasons, our knowledge of phloem–insect/pathogen interactions remains fragmentary. We highlight recent progress and areas of deficiency in the study of phloem-associated prokaryotic pathogens and insects. Increased efforts are needed to make major advances in this historically understudied area of research.
For the past 4 decades, intensive molecular studies of mostly leaf mesophyll cell-infecting pathogens and chewing insects have led to compelling models of plant–pathogen and plant–insect interactions. Yet, some of the most devastating pathogens and insect pests live in or feed on the phloem, a systemic tissue belonging to the plant vascular system. Phloem tissues are difficult to study, and phloem-inhabiting pathogens are often impossible to culture, thus limiting our understanding of phloem–insect/pathogen interactions at a molecular level. In this Perspective, we highlight recent literature that reports significant advances in the understanding of phloem interactions with insects and prokaryotic pathogens and attempt to identify critical questions that need attention for future research. It is clear that study of phloem–insect/pathogen interactions represents an exciting frontier of plant science, and influx of new scientific expertise and funding is crucial to achieve faster progress in this important area of research that is integral to global food security.
This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2015.
Author contributions: Y.J. and S.Y.H. designed research; Y.J. and S.Y.H. analyzed data; and Y.J., C.-X.Z., R.C., and S.Y.H. wrote the paper.
Reviewers: I.T.B., Max Planck Institute for Chemical Ecology (MPG); and G.C., University of California, Davis.
The authors declare no competing interest.
See QnAs on page 23371.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1915396116/-/DCSupplemental.
Published under the PNAS license.
