Jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA), collectively termed as jasmonates, are naturally occurring in plants and are important signal molecules involved in induced disease resistance and stress responses of plants. Besides their role in-planta, they are also rhizosecreted by root cells. Germinating soybean seeds exude large quantities of jasmonic acid; however there is no knowledge regarding how jasmonates influence cells of the soybean symbiont, Bradyrhizobium japonicum, in the rhizosphere. We studied the role of jasmonates in the soybean-Bradyrhizobium symbiosis. Bradyrhizobium japonicum cultures were induced with jasmonates and the resulting Nod factors were isolated and purified. Our results showed that JA and MeJA strongly induced the production of Nod factors by the tested B. japonicum strains. When added together, genistein and jasmonates resulted in greater LCO production than either one alone. Jasmonic acid is produced from linoleic and linolenic acids via the octadecanoid pathway; we studied the effect of these two fatty acids on B. japonicum nod gene induction. Interestingly both linoleic and linolenic acids induced the nod genes and caused LCO production by B. japonicum cultures. Since jasmonates induced the nod genes and also caused LCO production in B. japonicum, I conducted experiments in the greenhouse and field to determine whether incubation of B. japonicum with JA or MeJA prior to inoculation increases soybean nodulation variables and grain yield. Both genistein and McJA increased nodule number and nodule dry weight per plant. Due to enhanced nitrogen fixation, attributed to increased nodule number and weight, soybean dry matter accumulation and grain yield were increased. These results document the discovery of jasmonates and their precursors as new signal molecules in the Bradyrhizobium - soybean nitrogen fixing symbiosis.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.85574 |
| Date | January 2005 |
| Creators | Mabood, Fazli |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Plant Science) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002209346, proquestno: AAINR12894, Theses scanned by UMI/ProQuest. |
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