Research Focus

Strigolactones (SLs) are a novel plant hormone class that inhibits plant branching/tillering and performs several regulatory functions, including stem thickness, leaf senescence, and stress responses1. Meanwhile, root-released SLs also trigger seed germination in root parasitic weeds, such as Striga hermonthica, paving the way for host infestation1,2.  

Derived from carotenoids, SLs are characterized by a conserved butenolide ring (D-ring) essential for biological activity. This D-ring is linked via an enol-ether bridge to the rest of the SL molecule that has a variable structure: for canonical SLs, the enol-ether bridge is connected to a tricyclic lactone (the ABC-ring), whereas for the noncanonical SLs, it is bound to diverse and less defined structures1.

Albeit the progress that has been made in SL biology, the question of whether the two SL sub-families and their members have specific functions remains largely ambiguous2-5. The identification of the particular function(s) of each class of SL will allow the engineering of specific traits for plant architecture, increasing mycorrhization efficiency, and/or alleviating the infestation by root parasitic plants; however, the reasons and mechanisms of why plants synthesize and release different SLs remain elusive.

 To answer these questions, we will study rice mutants with different tillers and establish an SL analysis platform to examine their SL profiles. This will help us identify key single nucleotide polymorphisms (SNPs) in rice. Additionally, we will use CRISPR-Cas9 to generate rice mutants for validating chemical analysis and genomic functions. Beyond this, we aim to trace the original functions of both SL classes by investigating their biosynthesis pathways. This will give us deeper insights into why plants evolved such a diverse family of SL compounds.

References

1. Jian You Wang†, Guan-Ting Erica Chen†, Justine Braguy, and Salim Al-Babili. Distinguishing the Functions of Canonical Strigolactones as Rhizospheric Signals. (2024) TRENDS IN PLANT SCIENCE, 29(8), 925-936. https://doi.org/10.1016/j.tplants.2024.02.013 † These authors contributed equally.
2. Shinsaku Ito†, Justine Braguy†, Jian You Wang†, Akiyoshi Yoda, Valentina Fiorilli, Ikuo Takahashi, Muhammad Jamil, Abrar Felemban, Sho Miyazaki, Teresa Mazzarella, Guan-Ting Erica Chen, Akihisa Shinozawa, Aparna Balakrishna, Lamis Berqdar, Chakravarty Rajan, Shawkat Ali, Imran Haider, Yasuyuki Sasaki, Shunsuke Yajima, Kohki Akiyama, Luisa Lanfranco, Matias Zurbriggen, Takahito Nomura, Tadao Asami, and Salim Al-Babili. Canonical Strigolactones Are Not the Major Determinant of Tillering but Important Rhizospheric Signals in Rice. (2022) SCIENCE ADVANCES, 8, eadd1278 https://doi.org/10.1126/sciadv.add1278 † These authors contributed equally.
3. Guan-Ting Erica Chen†, Jian You Wang†, Cristina Votta †, Justine Braguy, Muhammad Jamil, Gwendolyn K Kirschner, Valentina Fiorilli, Lamis Berqdar, Aparna Balakrishna, Ikram Blilou, Luisa Lanfranco, and Salim Al-Babili. Disruption of the rice 4-DEOXYOROBANCHOL HYDROXYLASE unravels specific functions of canonical strigolactones. (2023) PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 120(42), e2306263120. https://doi.org/10.1073/pnas.2306263120 † These authors contributed equally.
4. Hendrik NJ Kuijer†, Jian You Wang†, Salim Bougouffa†, Michael Abrouk, Muhammad Jamil, Roberto Incitti, Intikhab Alam, Aparna Balakrishna, Derry Alvarez, Cristina Votta, Guan-Ting Erica Chen, Claudio Martínez, Andrea Zuccolo, Lamis Berqdar, Salim Sioud, Valentina Fiorilli, Angel R. de Lera, Luisa Lanfranco, Takashi Gojobori, Rod A Wing, Simon Krattinger, Xin Gao, and Salim Al-Babili. Chromosome-scale pearl millet genomes reveal CLAMT1b as key determinant of strigolactone pattern and Striga susceptibility. (2024) NATURE COMMUNICATIONS, 15(1), 1-12. https://doi.org/10.1038/s41467-024-51189-w † These authors contributed equally.
5. Jian You Wang, Aparna Balakrishna, Claudio Martínez, Guan-Ting Erica Chen, Salim Sioud, Angel R de Lera, and Salim Al-Babili. The rice orobanchol synthase catalyzes the hydroxylation of the non-canonical strigolactone methyl 4-oxo-carlactonoate. (2024) NEW PHYTOLOGIST, 244(6), 2121-2126. https://doi.org/10.1111/nph.20135