Effect Of Endogenous Jasmonic Acid On Arbuscular Mycorrhiza Formation In Tomato

Arbuscular mycorrhiza (AM) is the most widespread terrestrial symbiosis and is formedby at least80%of land plant species with fungi that belong to Glomeromycota. The AMhyphal network supply plants with nutrients (predominantly phosphate) and water, in turnobtain carbohydrates from plants. Therefore, AM symbiosis contributes significantly toglobal phosphate and carbon cycling and influences primary productivity in terrestrialecosystems. In addition, mycorrhizal can enhance markedly its host plant resistance topathogens and abiotic stresses. However, so far, the understanding of the mechanism of AMformation still remains limited due to the difficulty to cultivate the pure AM fungi, coupledwith the low frequency infection for the host and the lack of a synchronicity. Fortunately,recent studies demonstrate that several new plant hormones are involved directly in the AMformation, such as strigolactones and jasmonic acid (JA). In the case of JA, however, eventhough there are several lines of evidence including our previous study have shown thatendogenous JA or exogenous application of JA to plants play a crucial role in the symbiosisbetween hosts and AM fungi, the molecular mechanism by which JA regulates AM formationis less understood. In this study, tomato wild-type plants and its mutant spr2with JAdeficiency were used to comparatively investigate the role of endogenous JA in the AMformation between plant roots and AMF, with an emphasis on the function of JA levels andsystemic role of JA in above-ground parts in AM formation. Data were collected includingthe activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), andtheir isoenzymes shown by polyacrylamide gel electrophoresis (PAGE), malondialdehyde(MDA) contents, soluble sugar contents, and proline levels.The results showed that:1. The colonisation of AM in the spr2mutant was lower than that in wild-type plants,indicating that endogrnous JA in plants had a function in AM formation.2. JA in the above-ground parts of plants had a systemic function in AM formation.3. At the early stage of AF formation, the activities of SOD and CAT were reduced inwild-type plants relative to their uninoculated controls, suggesting that the inhibition of theseantioxidative enzymes was a prerequisite to the infection of AMF to plants.4. The MDA levels were higher in wild-type plants with high AM colonisation than in spr2with low AM colonisation, showing that the AM colonisation induce lipid peroxidation.5. The contents of proline and soluble sugar in wild-type plants were higher than thosein the spr2mutant plants after AM colonization, as well as in the non-inoculated control,together with the contents of proline and soluble sugar in the grafting plants with high AMcolonization being higher than those in the grafting plants with low AM colonization,indicating that the AM colonization was favourable for these soluble compounds productionsor accumulations in plants.