Crops worldwide are increasingly vulnerable to pandemics, as diseases hitch rides on global flows of people and goods, hopping from continent to continent. Phloem diseases such as citrus greening are one particularly devastating group of plant diseases that have been wreaking economic havoc globally. However, these diseases can be difficult to study, as phloem cells are relatively inaccessible and difficult to isolate. In work presented in a recent issue of Applications in Plant Sciences, Dr. Ed Etxeberria and colleagues at the University of Florida Citrus Research and Education Center present a new technique for identifying phloem cells in plant tissue.
In order to fight the devastation of phloem diseases, researchers must understand in detail the way these pathogens deform the plant phloem cells known as sieve elements and companion cells. Today, many basic questions remain unanswered about how diseases like citrus greening impact these phloem cells, which are essential for plant nutrient transport. As a first step in answering this question, phloem cells would have to be isolated. However, this presents a technical challenge, as phloem cells constitute less than 1% of total cells, are buried deep within plant tissues, and are interspersed with other cell types.
The technique presented here takes advantage of the distinctive anatomy of phloem cells by using organelle-specific dyes and fluorescent microscopy. For example, phloem cells called sieve element lack a nucleus and vacuole, but possess parietal mitochondria, so these cells become apparent when tissue is stained with the organelle-specific Hoechst 3342, Neutral Red, and MitoTracker Green and visualized with a fluorescent microscope. This method is applicable well beyond citrus, because it relies on the anatomy of phloem cells. That means it could be used to understand not only citrus greening but a wide variety of phloem diseases such as cucurbit yellow vine disease, corn stunt disease, and onion yellow dwarf disease.
Read more about this study at Science Daily.
citrus greening (Candidatus Liberibacter asiaticus): J.M. Bové, INRA Centre de Recherches de Bordeaux, Bugwood.org