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Nod factors secreted by nitrogen-fixing rhizobia are lipo-chitooligosaccharidic signals required for establishment of the nodule symbiosis with legumes. InMedicago truncatula, the Nod factor hydrolase 1 (MtNFH1) was found to cleave Nod factors ofSinorhizobium meliloti. Here, we report that the class V chitinase MtCHIT5b ofM. truncatulaexpressed inEscherichia colican release lipodisaccharides from Nod factors. Analysis ofM. truncatulamutant plants indicated that MtCHIT5b, together with MtNFH1, degradesS. melilotiNod factors in the rhizosphere.MtCHIT5bexpression was induced by treatment of roots with purified Nod factors or inoculation with rhizobia. MtCHIT5b with a fluorescent tag was detected in the infection pocket of root hairs. Nodulation of aMtCHIT5bknockout mutant was not significantly altered whereas overexpression ofMtCHIT5bresulted in fewer nodules. Reduced nodulation was observed whenMtCHIT5bandMtNFH1were simultaneously silenced in RNA interference experiments. Overall, this study shows that nodule formation ofM. truncatulais regulated by a second Nod factor cleaving hydrolase in addition to MtNFH1. 

Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio bursts,^[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the linkhttps://www.doi.org/10.57760/sciencedb.j00113.00076.