Category: Uncategorized

24 months passed – but we’re still here!

Look, I know we don’t get a lot of traffic to this site. Updating the lab webpage is not very high on my list of priorities. But a completely dead website doesn’t look great – and checking in once in a while proves I have not yet shuffled off this mortal coil.

So what’s new? In brief, a great end to 2023 with:

  1. Award of an ARC Discovery grant in collaboration with Prof Megan Ryan (UWA), Prof Phil Brewer (Uni Central Queensland) and Prof Caroline Gutjahr (Max Planck Institute for Molecular Plant Physiology). Naturally this was super exciting news! This project will investigate the role of butenolides in plant-fungal symbiosis in barley, one of our top Aussie crops.
  2. Publication of our paper in Current Biology: “Perception of butenolides by Bacillus subtilis via the α/β hydrolase RsbQ” led by Kim Melville and Muhammad Kamran, and with valuable contributions from Hugh and Maddy as well. The culmination of a considerable set of experiments that made up the body of Kim’s PhD thesis and learning how to grow and manipulate bacteria, rather than plants for a change. Thanks also to co-authors Max Costa and Nic Taylor for expertise in mass spec technologies. This was a massive achievement, and in the end the publishing experience was a very positive one. In summary: butenolides affect growth and energy stress in the common soil bacterium Bacillus subtilis – because it shares a similar butenolide receptor protein to those found in plants. The big question: do bacteria and plants communicate in some way through a common chemical signalling system?

2024 will be a big year – hoping to see a couple of PhD graduations from the lab and a couple more research papers. Stay tuned… if you’re patient!

Desmethyl butenolides – the new frontier?

I have been a bit remiss in updating the website but thought I would mention this one while I’m on here: the latest publication from the lab is recently published in New Phytologist, Hugh Yao as first author with valuable contributions from Frank and Kim as well. We think KAI2 proteins prefer to work with butenolide compounds that lack a methyl group, versus D14 proteins that require a methyl group. We used a couple of different compounds – GR24 and nitrile debranones – and showed that if you remove their respective methyl groups, they become much more active through KAI2. And most importantly, they become *specific* for KAI2 – they do not activate D14. So now we have a specific molecular feature that can be used to manipulate KAI2-dependent signalling. Most excellent.

2020 is the year that will be remembered.. for SMAX1

It was a behemoth, but Aashima Khosla, Dave Nelson and team at UC Riverside have published a tour de force analysing the functional domains of SMAX1, and showing how it is degraded in response to Karrikins and GR24. Jiaren (Hugh) and I contributed by showing that KAI2 degradation was dependent on SMAX1 and SMXL2, suggesting that the receptor and downstream repressor proteins form a complex and are possibly degraded together.

It was a pleasure to be part of this work – and congratulations to Aashima, Dave and others for an enormous effort that finally paid off. It’s rare to see such an admission in a manuscript, but I quote verbatim from the final paragraph of the introduction: “This proved to be an unexpectedly difficult undertaking”. Indeed it was.

Read the paper in The Plant Cell here. Here’s the full citation:

Khosla, A., Morffy, N., Li, Q., Faure, L., Chang, S., Yao, J., Zheng, J., Cai, M., Stanga, JP., Flematti, GR., Waters, MT., Nelson, DC. (2020). Structure-Function Analysis of SMAX1 Reveals Domains that Mediate its Karrikin-Induced Proteolysis and Interaction with the Receptor KAI2. The Plant cell


Our manuscript comes at a time of a veritable flurry of SMAX1 and SMXL-related publications from other groups, namely:

Wang, L., Xu, Q., Yu, H., Ma, H., Li, X., Yang, J., Chu, J., Xie, Q., Wang, Y., Smith, S., Li, J., Xiong, G., Wang, B. (2020). Strigolactone and Karrikin Signaling Pathways Elicit Ubiquitination and Proteolysis of SMXL2 to Regulate Hypocotyl Elongation in Arabidopsis thaliana. The Plant Cell

Bunsick, M., Toh, S., Wong, C., Xu, Z., Ly, G., McErlean, C., Pescetto, G., Nemrish, K., Sung, P., Li, J., Scholes, J., Lumba, S. (2020). SMAX1-dependent seed germination bypasses GA signalling in Arabidopsis and Striga Nature Plants

Wang, L., Wang, B., Yu, H., Guo, H., Lin, T., Kou, L., Wang, A., Shao, N., Ma, H., Xiong, G., Li, X., Yang, J., Chu, J., Li, J.(2020). Transcriptional regulation of strigolactone signalling in Arabidopsis Nature

Choi, J., Lee, T., Cho, J., Servante, E., Pucker, B., Summers, W., Bowden, S., Rahimi, M., An, K., An, G., Bouwmeester, H., Wallington, E., Oldroyd, G., Paszkowski, U. (2020). The negative regulator SMAX1 controls mycorrhizal symbiosis and strigolactone biosynthesis in rice. Nature Communications 11(1), 2114.

This corpus of work represents one of the biggest leaps forward in this field for some time, and constitutes a considerable collective achievement. Congratulations to everyone!