13/13 Thank you to my PhD supervisor, Wenbo, who always inspires scientists to climb new heights and to @thesainsburylab.bsky.social for being a wonderful place to do science.
Please read our preprint where we go into a lot more detail!

12/ Together, we show that, like in humans, plant proteases cleave bacterial OMPs as a defense strategy. We also reveal that PLCPs may be engineered to improve disease tolerance to HLB!
This project was a 6+ year effort requiring collaboration. Thank you to all authors!

11/ We also show that a PLCP called C14 can activate the defense gene PR1 only when LasOMP1 is also present and C14 is catalytically active. This suggests that PLCPs may release immune-activating peptides (PAMPs) from LasOMP1 in the plant!

10/ So PLCPs cleave LasOMP1 as an antimicrobial strategy?
Sadly, Las can’t be grown in the lab, so this can’t be directly tested…
…but we found that plants producing higher levels of CsRD21a (OE) appear healthier and have less Las growth (i.e. a higher CT value) than “normal” wild-type (WT) plants!

9/ …the answer is yes!
We detected LasOMP1 in HLB-infected (+Las) citrus and saw clear evidence that it is being cut into smaller peptides. Excitingly, we see that a PLCP called CsRD21a produces a similar peptide product in the lab (semi-in vitro)!
We dive much deeper into this in the paper. 😀

8/ LasOMP1 is produced at very high levels in both citrus and its insect host, called the Asian Citrus Psyllid, suggesting it may have an essential function to the bacterium.
Therefore, it is likely a good protein for the plant to destroy!
But is there evidence that PLCPs cleave LasOMP1...?

7/ First, we identified six predicted cell surface-exposed proteins, called outer membrane proteins (OMPs), in Las.
Interestingly, two PLCPs interact with LasOMP1, suggesting that this OMP may be targeted by PLCPs.

6/ To help fight HLB, we wanted to know how citrus PLCPs contribute to defense against the HLB bacterium, called Ca. Liberibacter asiaticus (Las).
We hypothesized that, like some human proteases, citrus PLCPs cleave cell surface-exposed proteins on the bacterium, thus suppressing infection.

5/ Citrus greening, also known as Huanglongbing or HLB, is a devastating and challenging disease to study. There is no cure, and increased climate threats are making a bad situation worse.

4/ For example, the bacterium that causes citrus greening disease inhibits proteases (specifically papain-like cysteine proteases or PLCPs) using a protein called SDE1, thus contributing to disease.
This suggests that citrus PLCPs may cleave something important that the bacterium needs!

3/ In humans, proteases can destroy proteins on the surface of harmful bacteria, causing them to shrivel up and die! Might plants do the same?

2/ Proteases are enzymes that chop up/cleave other proteins. We know that many plant pathogens block protease functions in their hosts to contribute to disease…
…but we know very little about how these proteases function (i.e. what they are cleaving)!

1/13 Thankfully, both you and your plants have a lot of sophisticated ways to fight off invading pathogens.
In our new preprint, we describe a new way in which animals and plants share a common strategy to ward off harmful bacteria.
www.biorxiv.org/content/10.1...

Surely you prefer rural Rhode Island for the Plant Proteolysis meeting?? 😉

Thank you, JJ!

🚨 PhD Opportunity!

🌿 Join us in Bristol to study plant-pathogen interactions!

👨‍🔬 Supervised by me @pierrebuscaill.bsky.social & Prof Thomas Gorochowski @chofski.bsky.social

📅 Apply by January 6th

🔗 More info: www.findaphd.com/phds/project...

📢 Please share!
#PhD #PlantImmunity #Microbiology

Very pleased to have passed my PhD viva today! Thank you Núria and @jonathandgjones.bsky.social for serving as my examiners and to Wenbo for your supervision and guidance! Has been a really great experience at @thesainsburylab.bsky.social!

Photo courtesy of @stephbornemann.bsky.social