Jasmonate Function & Mycorrhiza

As known from mutants defective in JA perception, jasmonates are important for the proper development of reproductive organs. In contrast to the JA-insensitive mutant of Arabidopsis thaliana showing a male-sterile phenotype, the JA-insensitive tomato mutant Sljai1 is female sterile and does not develop seeds (Fig. 1). It shows, however, additional alterations in the development of male flower organs: Sljai1 exhibits disturbed pollen development accompanied by increased stamen desiccation at later developmental stages. To elucidate the role of jasmonates in developing tomato flowers, we combine chemical, histochemical and molecular methods. Monitoring of JA occurrence, morphological differences and JA-dependent gene expression by transcript profiling in flower organs of wild type and jai1 led to insights into the flower-organ specific JA-responses. Regarding stamen development, we found that JA acts as positive regulator of pollen nutrition at early developmental stages and as an inhibitor of a premature function of ethylene at later stages to ensure proper timing in flower development (Dobritzsch et al., 2015). Genetic proof by creating double mutants of Sljai1 with an ethylene-insensitive mutant (NeverRipe) showed that ethylene insensitivity compensated partially missing JA function (Schubert et al., 2019b). Transcriptomics performed on ovules isolated from both WT and Sljai1 led to identification of a MYB transcription factor encoding gene (SlMYB21), which is highly expressed in WT, but almost not expressed in Sljai1. Slmyb21 mutants generated using CRISPR/Cas9 showed female sterility. Transcriptomics analysis from wild type, Sljai1 and Slmyb21 carpels revealed processes that might be controlled by SlMYB21 and demonstrated that SlMYB21 is involved in the control of flower development by JA (Schubert et al., 2019a). Further work will address the function of other JA-regulated transcription factors in tomato flower development as well as the identification of their targets. This work is funded in a collaborative project in frame of “Middle East Collaboration” by the DFG.

Dobritzsch, S.; Weyhe, M.; Schubert, R.; Dindas, J.; Hause, G.; Kopka, J.; Hause, B. (2015) Dissection of jasmonate functions in tomato stamen development by transcriptome and metabolome analyses. BMC Biol. 13, 28

Schubert, R., Dobritzsch, S., Gruber, C., Hause, G., Athmer, B., Schreiber, T., Marillonnet, S., Okabe, Y., Ezura, H., Acosta, I.F., Tarkowska, D., and Hause, B. (2019a). Tomato MYB21 acts in ovules to mediate jasmonate-regulated fertility. Plant Cell 31, 1043-1062

Schubert, R., Grunewald, S., von Sivers, L., and Hause, B. (2019b) Effects of jasmonate on ethylene function during the development of tomato stamens. Plants 8: 277