Review: Mekanisme Miko-Heterotrof Tumbuhan Monotropa

Monotropa merupakan Angiospermae yang tidak berkolofil sehingga tidak mampu untuk melakukan fotosintesis. Monotropa mendapatkan nutrisi untuk pertumbuhan dan perkembangannya melalui mekanisme miko-heterotrof, yaitu dengan berasosiasi dengan jamur mikoriza. Mikoriza bersimbiosis dengan akar tumbuhan autotrof untuk mendapatkan hasil fotosintesis, nutrisi tersebut kemudian ditransfer ke tumbuhan Monotropa. Sel-sel hifa yang berhubungan dengan epidermis akar tumbuhan autotrof dan Monotropa merupakan titik transfer nutrisi. Hifa mikoriza akan membentuk selubung (sheath) ke akar tumbuhan yang kemudian akan membentuk struktur hartig net yang menembus epidermis akar. Hartig net akan terus mengintrusi ke sel korteks akar yang kemudian akan membentuk fungal pegs. Fungal pegs ini yang akan menginduksi terbentuknya transfer sel untuk mentransfer nutrisi dari mikoriza ke Monotropa

Conversion from mutualism to parasitism: a mutant of the ectomycorrhizal agaricomycete Tricholoma matsutake that induces stunting, wilting, and root degeneration in seedlings of its symbiotic partner, Pinus densiflora, in vitro

Tricholoma matsutake is an ectomycorrhizal agaricomycete that produces matsutake mushrooms in association with conifers. Here, we isolated a pleiotropic mutant, designated as G1, following γ-ray irradiation of T. matsutake NBRC 33136. In addition to exhibiting increased cellulose- and amylose-degrading activities and altered mycelial morphology, G1 degenerated lateral roots and caused stunting or fatal wilting of seedlings of its symbiotic partner, Pinus densiflora, in vitro. A mutant, designated Ar 59, previously isolated after argon-ion beam irradiation, exhibited the same phenotypes as G1, but without its detrimental effects. Ar 59, like NBRC 33136, developed a Hartig net around healthy cortical cells that was composed of uniseriate hyphae. In G1-inoculated seedlings, the Hartig net was composed of heavily bundled hyphae penetrating the intercellular space, and it was accompanied by somewhat unusual forms of plant cortical cells. Sequences of rRNA gene-related markers, including four single nucleotide polymorphisms present within each strain, were 100% identical among NBRC 33136, G1, and Ar 59, indicating that they are mutants of the wild-type. Thus, γ-ray irradiation can convert the fungus from a beneficial to a harmful agent. These findings suggest the presence of an unknown mechanism in the fungal genome that can transform mutualism into parasitism.

Study on ectomycorrhizea of Siberian Pine (Pinus sibirica)

The ectomycorrhizal fungal community associated with Pinus Sibirica (Siberian Pine) in a Mongolian forest was investigated in this study. The ectomycorrhizaes were isolated from roots of Siberian pine and identified as Russulia Sardonia, Rhodocollybia butyracea, Tuber borchii, Tricholloma auratum and Lactarius deliciosus. Hartig net, external hyphae and mantle structures of ectomycorrhizae were observed in Siberian pine roots.Journal of agricultural sciences №15 (02): 123-129, 2015

Biosynthesis and Secretion of Indole-3-Acetic Acid and Its Morphological Effects on Tricholoma vaccinum-Spruce Ectomycorrhiza

ABSTRACTFungus-derived indole-3-acetic acid (IAA), which is involved in development of ectomycorrhiza, affects both partners, i.e., the tree and the fungus. The biosynthesis pathway, excretion from fungal hyphae, the induction of branching in fungal cultures, and enhanced Hartig net formation in mycorrhiza were shown. Gene expression studies, incorporation of labeled compounds into IAA, heterologous expression of a transporter, and bioinformatics were applied to study the effect of IAA on fungal morphogenesis and on ectomycorrhiza.Tricholoma vaccinumproduces IAA from tryptophan via indole-3-pyruvate, with the last step of this biosynthetic pathway being catalyzed by an aldehyde dehydrogenase. The geneald1was found to be highly expressed in ectomycorrhiza and induced by indole-3-acetaldehyde. The export of IAA from fungal cells is supported by the multidrug and toxic extrusion (MATE) transporter Mte1 found inT. vaccinum. The addition of IAA and its precursors induced elongated cells and hyphal ramification of mycorrhizal fungi; in contrast, in saprobic fungi such asSchizophyllum commune, IAA did not induce morphogenetic changes. Mycorrhiza responded by increasing its Hartig net formation. The IAA of fungal origin acts as a diffusible signal, influencing root colonization and increasing Hartig net formation in ectomycorrhiza.

A Fungal Conserved Gene from the Basidiomycete Hebeloma cylindrosporum Is Essential for Efficient Ectomycorrhiza Formation

We used Agrobacterium-mediated insertional mutagenesis to identify genes in the ectomycorrhizal fungus Hebeloma cylindrosporum that are essential for efficient mycorrhiza formation. One of the mutants presented a dramatically reduced ability to form ectomycorrhizas when grown in the presence of Pinus pinaster. It failed to form mycorrhizas in the presence of glucose at 0.5 g liter–1, a condition favorable for mycorrhiza formation by the wild-type strain. However, it formed few mycorrhizas when glucose was replaced by fructose or when glucose concentration was increased to 1 g liter–1. Scanning electron microscopy examination of these mycorrhizas revealed that this mutant was unable to differentiate true fungal sheath and Hartig net. Molecular analyses showed that the single-copy disrupting T-DNA was integrated 6,884 bp downstream from the start codon, of an open reading frame potentially encoding a 3,096-amino-acid-long protein. This gene, which we named HcMycE1, has orthologs in numerous fungi as well as different other eukaryotic microorganisms. RNAi inactivation of HcMycE1 in the wild-type strain also led to a mycorrhizal defect, demonstrating that the nonmycorrhizal phenotype of the mutant was due to mutagenic T-DNA integration in HcMycE1. In the wild-type strain colonizing P. pinaster roots, HcMycE1 was transiently upregulated before symbiotic structure differentiation. Together with the inability of the mutant to differentiate these structures, this suggests that HcMycE1 plays a crucial role upstream of the fungal sheath and Hartig net differentiation. This study provides the first characterization of a fungal mutant altered in mycorrhizal ability.

Hudsonia ericoides and Hudsonia tomentosa: Anatomy of mycorrhizas of two members in the Cistaceae from Eastern Canada

Most species in the family Cistaceae are found in the Mediterranean basin. Several hosts are of special interest, owing to their associations with truffle species, while many are important as pioneer plants in disturbed areas and in soil stabilization. For these reasons, understanding their root systems and their associated fungal symbionts is important. Most studies of the structure of mycorrhizas in this family involve two genera, Cistus and Helianthemum . The present study examines structural features of mycorrhizas in two North American species, Hudsonia ericoides L. and Hudsonia tomentosa Nutt. Root systems of both species are highly branched with most fine roots colonized by mycorrhizal fungi. Based on morphological features, several mycorrhizal fungi were identified; structural details also provided evidence of more than one fungal symbiont for each host species. All mycorrhizas had a multi-layered fungal mantle and Hartig net hyphae confined to radially elongated epidermal cells; no intracellular hyphae were observed. Although the Hartig net was confined to the epidermis, the outer row of cortical cell walls lacked suberin, a known barrier to fungal penetration. Mycorrhizas in H. ericoides and H. tomentosa differed from those of Cistus and Helianthemum species that have a Hartig net that extends into the root cortex, as well as frequently present intracellular hyphae.