The Root-Colonizing Endophyte Pirifomospora indica Confers Drought Tolerance in Arabidopsis by Stimulating the Expression of Drought Stress–Related Genes in Leaves

Abstract

Piriformospora indica is an endophytic fungus that colonizes the roots of many plant species, including Arabidopsis. We exposed 18-day-old Arabidopsis seedlings, which were either cocultivated with the fungus or mock-treated for the last 9 days, to mild drought stress for 84 h. During the first 36 to 48 h, seedlings cocultivated with the fungus continued to grow, while the uncolonized controls did not. This results in a threefold difference in the fresh weight and a more than twofold difference in the chlorophyll content. The photosynthetic efficiency was only slightly reduced in the colonized (F variable/F maximum [Fv/Fm] at t(0 h) = 0.82 and t(36 h) = 0.79) and was severely impaired in the uncolonized (Fv/Fm at t(0 h) = 0.81 and (t)(36 h) = 0.49) seedlings, which also showed symptoms of withering. When seedlings exposed to drought stress for 72 or 84 h were transferred to soil, 10% (72 h) and none (84 h) of uncolonized seedlings reached the flowering stage and produced seeds, while 59% (72 h) and 47% (84 h) of the colonized seedlings flowered and produced seeds. After exposure to drought stress for 3 h, the message levels for RESPONSE TO DEHYDRATION 29A, EARLY RESPONSE TO DEHYDRATION1, ANAC072, DEHYDRATION-RESPONSE ELEMENT BINDING PROTEIN2A, SALT-, AND DROUGHT-INDUCED RING FINGER1, phospholipase Ddelta, CALCINEURIN B-LIKE PROTEIN (CBL)1, CBL-INTERACTING PROTEIN KINASE3, and the histone acetyltransferase (HAT) were upregulated in the leaves of P. indica-colonized seedlings. Uncolonized seedlings responded 3 to 6 h later, and the message levels increased much less. We identified an Arabidopsis ethylmethane-sulfonate mutant that is less resistant to drought stress and in which the stress-related genes were not upregulated in the presence of P. indica. Thus, P. indica confers drought-stress tolerance to Arabidopsis, and this is associated with the priming of the expression of a quite diverse set of stress-related genes in the leaves. Transfer to soil was again associated with a faster and stronger upregulation of the message levels for phospholipase Ddelta, CBL1, and HAT in P. indica-colonized seedlings, indicating that this response might also contribute to better survival on soil.

Verticillium Infection Triggers VASCULAR-RELATED NAC DOMAIN7–Dependent de Novo Xylem Formation and Enhances Drought Tolerance in Arabidopsis

“…Moreover, plants protected by Piriformospora showed higher survival rates after drought stress treatments. Sherameti et al (2008) compared expression profiles of colonized and uncolonized Arabidopsis and observed a significantly faster and stronger response of the drought stress marker genes RD29A, ANAC072 (RD26), DREB2A, and PLDd in Piriformospora-colonized plants compared with noncolonized plants (it should be noted that RD29A and RD29B, the latter used in the current study, are both drought-and ABA-responsive genes, although they have slight differences in expression). The authors concluded that Piriformospora primes plants to counteract drought stress.…”

“…Subsequent GUS and LUC reporter assays revealed that Verticillium infection indeed alleviates drought stress under conditions of restricted water supply ( Figures 6A and 6B). This observation was corroborated by the reduced expression of the drought stress marker genes RE-SPONSIVE TO DESICCATION29B (RD29B; Christmann et al, 2005), ARABIDOPSIS NAC DOMAIN CONTAINING PROTEIN72 (ANAC072/RD26), DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN2A (DREB2A), and ARABIDOPSIS THALI-ANA PHOSPHOLIPASE D DELTA (PLDd) (Sherameti et al, 2008) in Verticillium-infected plants ( Figures 6C to 6F). …”

“…Piriformospora indica, a soilborne, endophytic fungus that was identified in desert plants (Verma et al 1998), also improves drought tolerance of Arabidopsis (Sherameti et al 2008). Piriformospora-colonized plants exposed to severe drought stress exhibited higher fresh weights than noncolonized plants, and photosynthetic activity was less impaired.…”

Functions of Novel Symbiotic Fungus - Piriformospora Indica

“…Co-inoculation with P. indica increased the drought tolerance levels in Arabidopsis [21] and Hordeum vulgare [22]. P. indica increased the general stress tolerance of plants by elevating the levels of antioxidative enzymes [23].…”

Challenges of climate change

“…Subsequently, it was established that the fungus promotes acquisition of drought tolerance in plants. 89,90 In contrast with arbuscular mycorrhizal fungi, it can be easily cultivated in axenic culture where it produces chlamydospores. [91][92][93] It is easily cultivated on a number of synthetic and complex media.…”