Abstract
Flowering in plants is synchronized by both environmental cues and internal regulatory factors. Previous studies have shown that the endophytic fungus Piriformospora indica promotes the growth and early flowering in Coleus forskohlii (a medicinal plant) and Arabidopsis. To further dissect the impact of P. indica on pathways responsible for flowering time in Arabidopsis, we co-cultivated Arabidopsis with P. indica and used RT-qPCR to analyze the main gene regulation networks involved in flowering. Our results revealed that the symbiotic interaction of Arabidopsis with P. indica promotes early flower development and the number of siliques. In addition, expression of the core flowering regulatory gene FLOWERING LOCUS T (FT), of genes controlling the photoperiod [CRYPTOCHROMES (CRY1, CRY2) and PHYTOCHROME B (PHYB)] and those related to gibberellin (GA) functions (RGA1, AGL24, GA3, and MYB5) were induced by the fungus, while key genes controlling the age and autonomous pathways remained unchanged. Moreover, early flowering promotion conferred by P. indica was promoted by exogenous GA and inhabited by GA inhibitor, and this effect could be observed under long day and neutral day photoperiod. Therefore, our data suggested that P. indica promotes early flowering in Arabidopsis likely through photoperiod and GA rather than age or the autonomous pathway.
Highlights
The root endophyte fungus P. indica is a basidiomycete of the Sebacinaceae family and mimics arbuscular mycorrhizal fungi (AMF) in many aspects[1]
The number of siliques produced by four investigated Arabidopsis ecotypes Ler, Col, C24, and Cvi-0 was ~2-fold higher in the presence of the fungus (Fig 1C)
Similar results were obtained for plants grown in sterile cultures, and we observed that Ler, Col, Cvi-0, and C24 plants inoculated by P. indica flowered 5 to 6 days earlier than those grown without P. indica inoculation (Fig 2)
Summary
The root endophyte fungus P. indica is a basidiomycete of the Sebacinaceae family and mimics arbuscular mycorrhizal fungi (AMF) in many aspects[1]. P. indica can colonize the roots of a broad range of hosts including monocot and dicot plants. It enhances the tolerance of colonized plants against drought, acidity, heavy metals, and various other abiotic stresses as well as biotic stresses[1,2,3,4,5,6,7,8]. In contrast to AMF, P. indica can be cultivated in axenic culture, and it could be very useful for crop improvement and sustainable agriculture[4].
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