Libo Shan

Christine Richardson Professor in Agriculture
Chancellor EDGES Fellow
Professor | Biochemistry & Biophysics

plant disease resistance, pathogen virulence, crop biotechnology, signal transduction, protein phosphorylation, ubiquitination.

Office:BICH / 302A

Earth is the planet of the plants. Being autotrophic, sessile, and long-living entities, plants have evolved fascinating strategies to cope with various environmental stresses. Our research is driven by the desire to understand the fundamental principles underlying plant disease resistance, and pathogen virulence, and to improve crop resilience to pathogen infections. We are probing the biochemical and genetic basis of plant signal transduction pathways from cell surface receptors sensing the presence of pathogens to signaling cascades and target genes and proteins that are central to launch effective immune responses in the context of balanced growth and development. We deploy cutting-edge molecular and biochemical technologies coupled with powerful genetic tractability of plants for discovering regulatory networks of living organisms fending off infections. In addition to the acquisition of foundational principles in biology, we further translate knowledge and platforms into the areas for the improvement of crop stress adaptation.

Activation and Attenuation of Plant Immune Signaling

Microbial signal perception by PRRs activates complex signaling events, culminating into a series of cellular and physiological responses with spatial and temporal dynamics. Some of responses occur instantaneously as early as seconds (sec) to minutes (min) or slowly as long as hours (hr) to days. Some responses are transiently induced whereas some are long lasting. The exemplary hallmark responses are shown with a time scale on the top. We are studying how the PRR signaling is activated and attenuated to mount balanced defense responses at biochemical and cellular levels. See Yu et al., 2017. Annu. Rev. Phytopathol. 55:109-137.

As a mechanism of intrinsic defense against invading pathogens, hosts have evolved cell surface-resident pattern recognition receptors (PRRs). These evolutionally convergent receptors are instrumental in the recognition of diverse pathogens, including bacteria, fungi, viruses, parasites, and insects. We are taking biochemical and molecular genetic approaches to study how the PRR complexes are activated and relay the signaling pathways to mount a series of seemly chaotic but harmonic cellular responses, contributing to plant resistance against a variety of pathogens. Also, we are deciphering how the immune responses are attenuated to avoid the defense responses from running amok.

Ma, X., Lucas, A.N.C., Leslie, E. M., Tao, K., Wu, Z., Liu, J., Xiao, Y., Li, B., Zhou, J., Savatin, V.D., Peng, J., Tyler, B., Heese, A., Russinova, E., He, P., and Shan, L. (2020) Ligand-induced monoubiquitination of BIK1 regulates plant immunity. Nature 581: 199-203.

Lin, W., Li, B., Lu, D., Chen, S., Zhu, N., He, P., and Shan, L. (2014) Tyrosine phosphorylation of BAK1/BIK1 mediates Arabidopsis innate immunity. Proc. Natl. Acad. Sci. U. S. A 111: 3632-3637.

Lu, D., Lin, W., Gao, X., Wu, S., Cheng, C., Avila, J., Heese, A., Devarenne, T., He, P., and Shan, L. (2011) Direct ubiquitination of pattern recognition receptor FLS2 attenuates plant innate immunity. Science. 332: 1439-1442.

Coordination of Plant Immunity, Growth and Development

In addition to microbial signals, plant hormones and endogenous peptides are perceived by the plasma membrane-localized LRR-RLK receptors. The ligand-activated LRR-RLKs rapidly recruit SERKs, and lead to diverse signaling outputs and physiological responses. Individual SERKs have specific and differential contributions to particular pathways. See Ma et al., Trends in Plant Science (2016) 21, 1017-1033.

Plant immune receptors PRRs are receptor-like kinases (RLKs) and receptor-like proteins (RLPs), many of which are implicated in sensing extrinsic and intrinsic signals, and govern diverse cellular responses. The signaling pathways mediated by leucine-rich repeat RLKs and RLPs converge at a small group of RLKs, namely somatic embryogenesis receptor kinases (SERKs), via ligand-induced heterodimerization and transphosphorylation. As shared coreceptors in diverse signaling receptorsomes, SERKs exhibit functional plasticity, yet maintain a high degree of signaling specificity. We are studying how SERKs function in plant immunity, cell death contamination, growth, and cell differentiation, and the regulation and activation mechanism of SERK-associated receptorsomes.

Yu, X., Xu, G., Li, B., de Souza Vespoli, L., Liu, H., Moeder, W., Chen, S., de Oliveira,M.V.V.,de Souza, S.A., Shao, W., Rodrigues, B., Ma, Y., Chhajed, S., Xue, S., Berkowitz, G.A., Yoshioka, K., He, P.,and Shan, L. (2019) The receptor kinases BAK1/SERK4 regulate Ca2+ channel-mediated cellular homeostasis for cell death containment. Current Biology 29: 3778-3790.

Zhou, J., Liu, D., Wang, P., Lin, W., Chen, S., Mishev, K., Lu, D., Kumar, R., Vanhoutte, I., He, P. Russinova, E., and Shan, L. (2018) Regulation of Arabidopsis brassinosteroid receptor BRI1 endocytosis and intracellular degradation by the E3 ubiquitin ligase PUB12/PUB13-mediated ubiquitination. Proc Natl Acad Sci U S A. 115: E1906-E1915.

Lin, W., Lu, D., Gao, X., Jian, S., Ma, X., Wang, Z., Mengiste, T., He, P., and Shan L. (2013) Inverse modulation of plant immunity and plant development by a receptor-like cytoplasmic kinase BIK1. Proc. Natl. Acad. Sci. U. S. A 110: 12114-12119.

Functional and Translational Genomics in Crop Stress Adaptation

Xanthomonas mediates bacterial blight susceptibility by targeting cotton GhSWEETS.  See Cox et al., Current Opinion in Plant Biology (2019) 50:95-103.

One of our ultimate goals for plant research is to develop ways to improve crop agricultural performance in a sustainable way. As an example, we have developed various functional genomic, cellular and biochemical platforms in cotton, which serves as a significant source of fiber, feed and oil products, to understand stress signaling and identify essential components to improve cotton resilience to pathogen infections, in particular fungal wilt pathogens and bacterial blight. In addition, we are collaborating with diverse expertise in engineering and medicine for bioremediation and biomedicine research.

Wang, P., Jamieson, P., Zhang, L., Zhao, Z., Shao, W., Wu, L.,Zhou, L., Mustafa, R., Amin, I., Hou, Y., He, P., and Shan, L. (2020) Cotton wall-associated kinase GhWAK7A mediates responses to fungal wilt pathogens by modulating chitin sensory complex. The Plant Cell

Cox, K. L., Babilonia, K., He, P., and Shan, L. (2019) Return of old foes – recurrence of bacterial blight and fusarium wilt of cotton. Current Opinion in Plant Biology 50: 95-103.  

Cox, K. L., Meng, F., Wilkins, K. E., Li, F., Wang, P., Booher, N. J., Chen, L. Q., Zheng, H., Gao, X., Zheng, Y., Fei, Z., Yu, J. Z., Isakeit, T., Wheeler, T., Frommer, W. B., He, P., Bogdanove, A. J., and Shan, L. (2017) TAL effector-mediated induction of a SWEET sucrose transporter confers susceptibility to bacterial blight of cotton. Nat Commun. 8:15588, DOI: 10.1038/ncomms15588.