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Author: search.filters.author.Raul, BikashSubject: search.filters.subject.Root nodule symbiosis

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    Nodule INception (NIN)-independent epidermal events lead to bacterial entry during nodule development in peanut (Arachis hypogaea)
    (John Wiley & Sons, 2022) Bhattacharjee, Oindrila; Raul, Bikash; Ghosh, Amit; Bhardwaj, Akanksha; Bandyopadhyay, Kaustav; Sinharoy, Senjuti
    Summary Legumes can host nitrogen-fixing rhizobia inside root nodules. In model legumes, rhizobia enter via infection threads (ITs) and develop nodules where infection-zone contains a mixture of infected and uninfected cells. Peanut (Arachis hypogaea) diversified from model legumes ~50-55 million years ago. Rhizobia enter through ‘cracks’ to form nodules in peanut roots where the cells of infection-zone are uniformly infected. Phylogenomic studies indicated symbiosis as a labile trait in peanut. These atypical features prompted us to investigate the molecular mechanism of peanut nodule development. Combining cell biology, genetics, and genomic tools, we visualized the status of hormonal signaling in peanut nodule primordia. Moreover, we dissected the signaling modules of Nodule INception (NIN), a master regulator of both epidermal infection and cortical organogenesis. Cytokinin signaling operates in a broad zone, from the epidermis to the pericycle inside nodule primordia, while auxin signaling is narrower and focused. NIN is involved in the nodule organogenesis, but not in the crack entry. Nodulation Pectate Lyase (NPL), which remodels cell walls during IT-formation, is not required. Whereas Nodule enhanced Glycosyl Hydrolases (AhNGHs) is recruited for cell wall modification during crack entry. While the hormonal regulation is conserved, the function of the NIN signaling modules is diversified in peanut.
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    An improvised hairy root transformation method for efficient gene silencing in roots and nodules of Arachis hypogaea
    (Springer Nature Publishing AG, 2022) Raul, Bikash; Sinharoy, Senjuti
    Peanut (Arachis hypogaea) is a major oilseed crop and is widely cultivated in tropical and subtropical climate zone worldwide. Peanut belongs to the Papilionoid family with an atypical nodule developmental program. In particular, rhizobia enter through developmental cracks and lead to the formation of aeschynomenoid subtype determinate nodules. Peanut nodules are efficient nitrogen-fixers and form swollen bacteroid containing symbiosomes. The allotetraploid genome and recalcitrance to stable transformation used to be the major bottleneck for peanut biologists. Recent genome sequencing of peanut cultivar Tifrunner has opened up a huge opportunity for molecular research. A composite plant contains transformed roots with a non-transformed shoot. The composite plant-based approach has already proven to be a tool of choice for high throughput studies in root biology. The available protocols failed to generate efficient hairy root transformation in the genome sequenced cultivar Tifrunner. Here we describe an efficient hairy root transformation and composite plant generation protocol for the peanut cultivar Tifrunner. Our protocol generated ~92% plant regeneration efficiency with between 21.8% and 58.6% co-transformed root regeneration. We also show that this protocol can be efficiently used for protein localization, promoter GUS analysis, monitoring hormone response, and RNAi mediated knockdown of the genes using genome sequenced cultivar Tifrunner.