Structure-specific regulation of nutrient absorption, metabolism and transfer in arbuscular mycorrhizal fungi

Abstract

Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with most land plants, mainly for the purpose of nutrient exchange. Many studies have revealed the regulation of absorption, metabolism, and transfer of nutrients in AMF and the genes involved in these processes. However, the spatial regulation of the genes among the structures comprising each developmental stage are not well understood. Here, we demonstrate the structure-specific transcriptome of the model AMF species, Rhizophagus irregularis. We performed an ultra-low input RNA-seq analysis, SMART-seq2, comparing five extraradical structures, germ tubes, runner hyphae, branched absorbing structures, immature spores, and mature spores. In addition, we reanalyzed the recently reported RNA-seq data comparing intraradical hyphae and arbuscules. Our analyses captured the distinct features of each structure and revealed the structure-specific expression patterns of genes related to absorption, metabolism, and transfer of nutrients. Of note, the transcriptional profiles suggest the distinct functions of branched absorbing structures in nutrient absorption. These findings provide a comprehensive dataset to advance our understanding of the transcriptional dynamics of fungal nutrition in this symbiotic system.

Ciências biológicas: as diversas manifestações da vida

“…The absorption of phosphate by the fungus from the soil solution is probably associated with a cotransport system, in which the H + and Na + ions are transported together with the inorganic phosphate (Tatsuhiro et al, 2016;Kameoka et al, 2019). After absorption of phosphate from the soil solution, it is transferred from the cytoplasm to vacuoles within the extraradical hyphae, through an electric potential gradient created by the vacuolar H + -ATPase (V-ATPase) (Fellbaum et al, 2014).…”

“…The polyphosphate in the intraradical hyphae is longer than that in the extraradical hyphae or spores, indicating that the molecule is depolymerized before the transference in the periarbuscular space (Ohtomo and Saito, 2005;Kameoka et al, 2019).…”

“…Nitrogen is absorbed by AMF extraradical hyphae as nitrate or ammonium. Studies have been suggested that the capture system has five times more affinity with NH 4 + (Bücking and Kafle, 2015; Kameoka et al, 2019), and within the hyphae, they are converted into glutamine compounds (Tatsuhiro et al, 2016).…”

“…Vacuolar calcium is the main source of Ca 2+ storage in AMF hyphae (Tatsuhiro et al, 2016). Two carriers perform complementary functions in sequestrating Ca 2+ in the vacuole: Vcx1p, a low-affinity Ca 2+ /H + exchanger, which rapidly sequestrates Ca 2+ in the vacuole, and Pmc1p, a high-affinity Ca 2+ ATPase required to maintain the low calcium concentration in the cytosol (Liu et al, 2013;Kameoka et al, 2019). This element is essential for the establishment and maintenance of mycorrhization by mediating intracellular signaling in perinuclear membranes, forming a rhythmic flow of calcium in the nuclear membrane (calcium spiking), which triggers the transcriptional reprogramming in host cells (Oldroyd and Downie, 2006).…”