Plant Germline Antiviral Immunity

Our group, led by Dr. Marco Incarbone, is interested in plant host-virus interactions and more specifically those occurring in plant stem cells and reproductive tissues. Understanding these interactions is extremely important, since they determine whether a viral infection is transmitted from parent to progeny or not.

Since viruses were discovered in plants at the end of the 19th century a lot of research has focused on understanding the molecular mechanisms regulating viral infections, which cause serious damage to agriculture worldwide. These efforts have allowed the understanding of many of these processes, yet certain fundamental aspects of infection remain quite mysterious. It has been known for almost a century that many viruses, despite being able to rapidly infect whole host plants, do not infect the stem cells in the shoot apical meristem and are not (or scarsely) transmitted vertically to the host progeny following sexual reproduction. Since the gametes (germline) develop from the meristematic stem cells, exclusion of viruses from the former and the latter are believed to be connected, hinting to the existence of exceptionally potent antiviral barriers in these crucial cell types. It is very important to understand these antiviral defenses, both for the sake of crop protection and our understanding of virology.

The investigation of these fascinating aspects of biology is very challenging for multiple reasons. For example, the cells involved are very few and often deeply embedded within larger tissues, making it hard to isolate and study them. In addition, viral infections are very dynamic and time-sensitive processes, so precisely “catching” the virus-germline interactions as they occur can be quite tricky. To face these challenges we are using several innovative experimental approaches and state-of-the-art technologies, such as RNA sequencing in rare/single cells and live microscopy, while developing their use for plant virology investigation. Due to its experimental tractability, we mainly use the model plant species Arabidopsis thaliana along with a variety of RNA viruses infecting it. To translate our discoveries to crop science we are also expanding our investigation to tomato and rice.

Our research mainly focuses on the following questions:

  • Which host genes restrict or allow virus infection of stem cells and germline?
  • RNA interference is known to exclude viruses from stem cells and to be somehow involved in germline defense. Viruses are able to block RNA interference in the rest of the plant, so why are they unable to do so in these particular cell types?
  • The hormone salicylic acid is known to be involved in stem cell immunity, acting as an “alarm bell” and activating stem cell-specific defenses. How and where does this happen in the plant?
  • Certain virus species, known as cryptic/persistent viruses and very poorly understood, are transmitted from parent to progeny through generations and thought to be omnipresent in the meristems and germlines of their hosts. Why and how are they tolerated?

We are also passionate about many other related questions and are keen to collaborate with labs around the world to expand our experimental portfolio and expertise.

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