Seminars

Research in our laboratory focuses on the developmental genetics of plant reproduction, with an emphasis on epigenetic gene regulation and cell-cell communication during double fertilization. Fertilization depends on the proper reception of the pollen tube by the synergid cells, involving a complex interplay mediated by calcium signaling [1]. We have shown that receptor kinases of the CrRLK1L subfamily play an important role in reproduction, with the FERONIA receptor kinase acting in the synergids to mediate proper pollen tube reception [2,3]. The extracellular domain of CrRLK1Ls has similarities with malectin [4], suggesting it binds carbohydrate moieties, but it was also reported to bind secreted RALF and peptides [5-7]. Thus, the functions of CrRLK1Ls are diverse and complex. We are currently investigating the events occurring immediately prior to fertilization once the pollen tube interacts with the synergid cell. Upon proper pollen tube reception, the pollen tube ruptures and releases the two sperm cells to effect double fertilization. How exactly fertilization triggers the development of the two fertilization products, the embryo and endosperm, is still not well understood. We have recently shown that a paternally delivered factor plays a crucial role in activating endosperm development [8]. In this seminar, I will report on our progress in deciphering the signals and underlying mechanisms that control these important steps in plant reproduction.

References:
[1] Ngo QA, Vogler H, Lituiev DS, Nestorova A, Grossniklaus U (2014). A calcium dialog mediated by FERONIA signal transduction controls plant sperm delivery. Dev Cell 29, 491-500. 
[2] Huck N, Moore JM, Federer M, Grossniklaus U (2003). The Arabidopsis mutant feronia disrupts the female gametophytic control of pollen tube reception. Development 130, 2149-2159. doi: 
[3] Escobar-Restrepo JM, Huck N, Kessler S, Gagliardini V, Gheyselinck J, Yang WC, Grossniklaus U (2007). The FERONIA receptor-like kinase mediates male-female interactions during pollen tube reception. Science 317:656-660.
[4] Boisson-Dernier A, Kessler SA, Grossniklaus U (2011). The walls have ears: the role of plant CrRLK1Ls in sensing and transducing extracellular signals. J Exp Bot 62, 1581-1591.
[5] Mecchia M, Santos-Fernandez G, Duss NN, Somoza SC, Boisson-Dernier A, Gagliardini V, Martínez-Bernardini A, Ndinyanka Fabrice T, Ringli C, Muschietti JP, Grossniklaus U (2017) RALF4/19 peptides interact with LRX proteins to control pollen tube growth in Arabidopsis. Science 358, 1600-1603.
[6] Ge Z, Bergonci T, Zhao Y, Zou Y, Du S, Liu MC, Luo X, Ruan H, García-Valencia LE, Zhong S, Hou S, Huang Q, Lai L, Moura DS, Gu H, Dong J, Wu HM, Dresselhaus T, Xiao J, Cheung AY, Qu LJ (2017). Arabidopsis pollen tube integrity and sperm release are regulated by RALF-mediated signaling. Science 358, 1596-1600.
[7] Moussu S, Broyart C, Santos-Fernandez G, Augustin S, Wehrle S, Grossniklaus U, Santiago J (2020) Structural basis for recognition of RALF peptides by LRX proteins during pollen tube growth. Proc Natl Acad Sci USA 117, 7494-7503. 
[8] Simonini S, Bencivenga S, Grossniklaus U (2024). A paternal signal induces endosperm proliferation upon fertilization in Arabidopsis. Science 383, 646-653.