Plant volatile emissions can recruit predators of herbivores for indirect defence and attract pollinators to aid in pollination. Although volatiles involved in defence and pollinator attraction are primarily emitted from leaves and flowers, respectively, they will co‐evolve if their underlying genetic basis is intrinsically linked, either due to pleiotropy or genetic linkage. However, direct evidence of co‐evolving defence and floral traits is scarce.
We characterized intra‐specific variation of herbivory‐induced plant volatiles (HIPVs), the key components of indirect defence against herbivores, and floral volatiles in the wild tobacco Nicotiana attenuata. We found that variation of (E )‐β‐ocimene and (E )‐α‐bergamotene contributed to the correlated changes in HIPVs and floral volatiles among N. attenuata natural accessions. Intra‐specific variations of (E )‐β‐ocimene and (E )‐α‐bergamotene emissions resulted from allelic variation of two genetically co‐localized terpene synthase genes, NaTPS25 and NaTPS38 respectively. Analyzing haplotypes of NaTPS25 and NaTPS38 revealed that allelic variations of NaTPS25 and NaTPS38 resulted in correlated changes of (E )‐β‐ocimene and (E )‐α‐bergamotene emission in HIPVs and floral volatiles in N.  attenuata.
Together, these results provide evidence that pleiotropy and genetic linkage result in correlated changes in defences and floral signals in natural populations, and the evolution of plant volatiles is likely under diffuse selection.

Original publication:
Xu, S., Kreitzer, C., McGale, E., Lackus, N.D., Guo, H., Köllner, T.G., Schuman, M.C., Baldwin, I.T. and Zhou, W. (2020), Allelic differences of clustered terpene synthases contribute to correlated intra‐specific variation of floral and herbivory‐induced volatiles in a wild tobacco. New Phytol. Accepted Author Manuscript. doi:10.1111/nph.16739

Many flowering plants produce highly diverse and specific floral scents that are important for mediating interactions with their pollinators and/or herbivores. The well-known fitness effects and extraordinary diversity of floral scents provide an excellent system for studying the evolution of novel adaptive traits in plants. However, very few studies have revealed how plants evolve new floral scents.

In this study, a group of scientists from Max Planck Institute for Chemical Ecology and University of Münster uncovered the biosynthetic machinery and evolution of a species-specific nocturnal floral volatile of a wild tobacco (Nicotiana attenuata): benzyl acetone (BA), a compound that mediates both pollinator attraction and florivore deterrence. They demonstrated that three genes, NaPAL4, NaIFR3, and NaCHAL3 are sufficient and necessary for the BA biosynthesis in N. attenuata. They also found that while independent changes in transcription in all three genes contributed to intraspecific variations of floral BA emission, the gain of expression of NaIFR3 resulted in the biosynthesis of BA, which was only found in N. attenuata. Because NaIFR3 evolved from a gene duplication that occurred earlier than the diversification of Nicotiana, this study provided an example that novel metabolic pathways can arise via altering the expression of existing genes.

The study not only revealed how novel adaptive traits have been evolved, but also shows different genetic mechanisms are involved in intra- and interspecific variations of adaptive traits. Scientists found that while all three biosynthetic genes contributed to the intraspecific variations of floral BA emission, only the expression changes in NaIFR3 contributed to differences in floral BA emission among closely related species. The results indicate that adaptive traits might evolve differently between and within species.

The study showed that a new metabolic pathway can arise via expression changes in a single gene. Such mechanism might not only explain the evolution of amazing diversity of specialized metabolites in plants, but also demonstrated the potential of using metabolic engineering in crop development and protection.

Original publication:
Han Guo, Nathalie D Lackus, Tobias G Köllner, Ran Li, Julia Bing, Yangzi Wang, Ian T Baldwin, Shuqing Xu, Evolution of a Novel and Adaptive Floral Scent in Wild Tobacco, Molecular Biology and Evolution, , msz292, https://doi.org/10.1093/molbev/msz292

We challenge ourselves & help each other.

She will study how insecticide induced behavior changes affect pesticide resistance in Colorado potato beetles. Welcome Alitha.

Machine learning reveals the underlying mechanisms of alternative splicing evolution in plants. The paper is now published (https://doi.org/10.3389/fpls.2019.00707). Congratulations to Zhihao and other co-authors!

A key take home message: Teamwork is fun.

This month, we have two new group members: Mr. Yangzi Wang and Ms. Marie Sarazova. Yangzi joined us as a PhD student. He will work on plant evolutionary genomics. Marie joined us as a technician. She will provide many supports on different ongoing research projects in the group. Wellcome Yangzi and Marie.

A paper co-authored by Shuqing Xu showed that the CRISPR-mediated gene editing works in duckweeds.
The paper is now online: [a1] https://onlinelibrary.wiley.com/doi/abs/10.1111/pbi.13128
The S. polyrhiza genome editing is on the way.

Duckweeds – for many aquatic animals like ducks and snails, a treat, but for pond owners, sometimes a thorn in the side. The tiny and fast-growing plants are of great interest to researchers, and not at least because of their industrial applications – for example, to purify wastewater or generate energy. An international research team from Münster, Jena (both Germany), Zurich (Switzerland) and Kerala (India) have recently studied the genomics of the giant duckweed. They discovered that genetic diversity, i.e. the total number of genetic characteristics that are different among individuals, is very low. “This is remarkable given that their population size is very large – there can, for example, be millions of individuals in a single pond”, says Shuqing Xu, professor for plant evolutionary ecology at the University of Münster and lead author of the study.

To read the full article on the publication follow this link to the main page of the university.

Original publication:
S. Xu et al. (2019): Low genetic variation is associated with low mutation rate in the giant duckweed. Nature Communications; DOI: 10.1038/s41467-019-09235-5

Further information
Original publication in "Nature Communications"
Plant Adaptation-in-action Group at Münster University
Emerging field “Evolution” at Münster University

On 2nd August, Ms. Lanlan Ke from Fujian Agriculture and Forestry University joined our group as a visiting student. She will work on illustrating the level of pleiotropy among singling networks in tomato. Welcome Lanlan and have a good start!

Shuqing Xu gave a plenary talk about plant defence evolution at the 12th Chinese Chemical Ecology Conference in Fuzhou, China.

Xu lab started officially at the Institute of Evolution and Biodiversity, University of Münster.
We look forward to work together with colleagues and students in the University. We study plant adaption-in-action!