QUI-GON JINN, a member of the YODA family, plays a role during female reproduction in Arabidopsis thaliana [résumé] V International APOMIXIS 2025 Conference : book of abstracts Siena, L.A. /Michaud, Caroline Colono, C. Sol Vega, M. Ortiz, J.P.A. Pessino, S.C. /Leblanc, Olivier Paspalum notatum, a subtropical forage grass native to South America, has proven to be a fruitful model for studying apomixis in plants. Several genes associated with apomixis have been identified through genetic mapping and comparative mRNA analyses, including QUI-GON JINN (QGJ) encoding a MAPK3 protein of the YODA family. Interestingly, the downregulation of QGJ in P. notatum apomictic genotypes has been associated with a decrease in the number of unreduced (aposporous) embryo sacs. To disclose QGJ function during sexual development, we have undertaken its functional characterization in the model plant Arabidopsis thaliana using genetic and cellular approaches. The protein accumulation generated by GUS reporter lines indicated that QGJ is expressed during ovule development and accumulates in the L1 cell layer of the ovule primordium, but not in the placenta. QGJ is also expressed in degenerating megaspores, while functional megaspores completely lack signal. Finally, in developing seeds, the endosperm showed GUS accumulation, but the zygote and growing embryos were completely devoid of signal. Furthermore, qgj defective mutants led to reproductive alterations of the female development, in a manner reminiscent of apomixis. Furthermore, qgj mutants showed alterations during female meiosis, female gametophytic development and early seed development. These results indicate that QGJ is expressed during megasporogenesis and endosperm development, and suggest that its function is related with megaspore degeneration in the tetrad, gametophyte development and non-cell autonomous control of embryo development. IRD DIADE /Leblanc, Olivier (ed.) /Autran, Daphné (ed.) 2025 text https://www.documentation.ird.fr/hor/fdi:010096562 fdi:010096562 Siena L.A., Michaud Caroline, Colono C., Sol Vega M., Ortiz J.P.A., Pessino S.C., Leblanc Olivier. QUI-GON JINN, a member of the YODA family, plays a role during female reproduction in Arabidopsis thaliana [résumé]. In : Leblanc Olivier (ed.), Autran Daphné (ed.), . V International APOMIXIS 2025 Conference : book of abstracts IRD ; DIADE, 2025, 47 International APOMIXIS 2025 Conference, 5., Montpellier (FRA), 2025/09/16-19 EN AMERIQUE DU SUD