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Brassinosteroids play multiple roles in nodulation of pea via interactions with ethylene and auxin


McGuiness, PN and Reid, JB and Foo, E, Brassinosteroids play multiple roles in nodulation of pea via interactions with ethylene and auxin, Planta, 252, (4) Article 70. ISSN 0032-0935 (2020) [Refereed Article]

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DOI: doi:10.1007/s00425-020-03478-z


Nodulation, the symbiosis between legumes and rhizobial bacteria, is regulated by a suite of hormones including brassinosteroids. Previous studies have found that brassinosteroids promote nodule number by inhibiting ethylene biosynthesis. In this study, we examined the influence of brassinosteroids on the various stages of infection and nodule development. We utilise pea mutants, including brassinosteroid mutants lk, lka and lkb, the ethylene insensitive ein2 mutant and the lk ein2 double mutant, along with transgenic lines expressing the DR5::GUS auxin activity marker to investigate how brassinosteroids interact with ethylene and auxin during nodulation. We show that brassinosteroids inhibit the early stages of nodulation, including auxin accumulation, root hair deformation and infection thread formation, and demonstrate that infection thread formation is regulated by brassinosteroids in an ethylene independent manner. In contrast, brassinosteroids appear to act as promoters of nodule initiation through both an ethylene dependent and independent pathway. Although brassinosteroids positively influence the ultimate number of nodules formed, we found that brassinosteroid-deficiency did not influence nodule structure including the vascular pattern of auxin activity or nitrogen-fixation capacity. These findings suggest that brassinosteroids are negative regulators of infection but positive regulators of nodule initiation. Furthermore, brassinosteroids do not appear to be essential for nodule organogenesis or function. Given the influence of brassinosteroids on discreet stages of nodulation but not nodule function, manipulation of brassinosteroids may be an interesting avenue for future research on the optimisation of nodulation.

Main conclusion: A comprehensive analysis of the role of brassinosteroids in nodulation, including their interactions with auxin and ethylene revealed that brassinosteroids inhibit infection, promote nodule initiation but do not influence nodule organogenesis or function.

Item Details

Item Type:Refereed Article
Keywords:auxin, brassinosteroid, ethylene, nodulation, nitrogen fixation, pea
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Plant developmental and reproductive biology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Other plant production and plant primary products
Objective Field:Other plant production and plant primary products not elsewhere classified
UTAS Author:McGuiness, PN (Mr Peter McGuiness)
UTAS Author:Reid, JB (Professor Jim Reid)
UTAS Author:Foo, E (Associate Professor Eloise Foo)
ID Code:144738
Year Published:2020
Funding Support:Australian Research Council (DP190101817)
Web of Science® Times Cited:4
Deposited By:Plant Science
Deposited On:2021-06-07
Last Modified:2021-08-17

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