Mechanisms of the IAA and ACC-deaminase producing strain of Trichoderma longibrachiatum T6 in enhancing wheat seedling tolerance to NaCl stress

Abstract

BackgroundTrichoderma species, a class of plant beneficial fungi, may provide opportunistic symbionts to induce plant tolerance to abiotic stresses. Here, we determined the possible mechanisms responsible for the indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate-deaminase (ACC-deaminase) producing strain of Trichoderma longibrachiatum T6 (TL-6) in promoting wheat (Triticum aestivum L.) growth and enhancing plant tolerance to NaCl stress.ResultsWheat treated with or without TL-6 was grown under different levels of salt stress in controlled environmental conditions. TL-6 showed a high level of tolerance to 10 mg ml− 1 of NaCl stress and the inhibitory effect was more pronounced at higher NaCl concentrations. Under NaCl stress, the activity of ACC-deaminase and IAA concentration in TL-6 were promoted, with the activity of ACC-deaminase increased by 26% at the salt concentration of 10 mg ml− 1 and 31% at 20 mg ml− 1, compared with non-saline stress; and the concentration of IAA was increased by 10 and 7%, respectively (P < 0.05). The increased ACC-deaminase and IAA concentration in the TL-6 strain may serve as an important signal to alleviate the negative effect of NaCl stress on wheat growth. As such, wheat seedlings with the ACC-deaminase and IAA producing strain of TL-6 treatment under NaCl stress increased the IAA concentration by an average of 11%, decreased the activity of ACC oxidase (ACO) by an average of 12% and ACC synthase (ACS) 13%, and decreased the level of ethylene synthesis and the content of ACC by 12 and 22%, respectively (P < 0.05). The TL-6 treatment decreased the transcriptional level of ethylene synthesis genes expression, and increased the IAA production genes expression significantly in wheat seedlings roots; down-regulated the expression of ACO genes by an average of 9% and ACS genes 12%, whereas up-regulated the expression of IAA genes by 10% (P < 0.05). TL-6 treatments under NaCl stress decreased the level of Na+ accumulation; and increased the uptake of K+ and the ratio of K+/Na+, and the transcriptional level of Na+/H+ antiporter gene expression in both shoots and roots.ConclusionsOur results indicate that the strain of TL-6 effectively promoted wheat growth and enhanced plant tolerance to NaCl stress through the increased ACC-deaminase activity and IAA production in TL-6 stain that modulate the IAA and ethylene synthesis, and regulate the transcriptional levels of IAA and ethylene synthesis genes expression in wheat seedling roots under salt stress, and minimize ionic toxicity by disturbing the intracellular ionic homeostasis in the plant cells. These biochemical, physiological and molecular responses helped promote the wheat seedling growth and enhanced plant tolerance to salt stress.

Trichoderma parareesei Favors the Tolerance of Rapeseed (Brassica napus L.) to Salinity and Drought Due to a Chorismate Mutase

“…Nonetheless, we have observed how the rapeseed-root-inoculation with Trichoderma also increases its tolerance against drought ( Figure 1B) and salinity ( Figure 1C)-demonstrated in its productivity. Similarly, an increase in the salt-tolerance was observed with the inoculation of tomatoes with T. harzianum [16,19] and T. parareesei [24], of cucumber with T. harzianum [52], and of wheat with T. longibrachiatum [53,54]; also, regarding drought-tolerance, with the inoculation of tomato with T. longibrachiatum or T. harzianum [55,56]-never before analyzed in the case of rapeseed.…”

Endophytic fungus Falciphora oryzae promotes lateral root growth by producing indole derivatives after sensing plant signals

“…Although not as common as that in growth‐promoting bacteria, auxin has been shown to be produced by various beneficial fungi to promote plant root growth and biomass (Li et al, ; Sardar & Kempken, ; Zhang, Gan, & Xu, ), for example, the free‐living beneficial fungus T. virens and T. atroviride promote lateral root growth in Arabidopsis , and the growth‐promoting effect is reduced in mutants that are defective in auxin signalling and transport. The auxin‐related compounds IAA, indole‐3‐acetaldehyde, and indole‐3‐ethanol have been detected in the supernatant of Trichoderma virens and Trichoderma atroviride liquid cultures upon the addition of tryptophan (Contreras‐Cornejo et al, ).…”

“…Although not as common as that in growth-promoting bacteria, auxin has been shown to be produced by various beneficial fungi to promote plant root growth and biomass (Li et al, 2018;Sardar & Kempken, 2018;Zhang, Gan, & Xu, 2019), for example, the free-living Transcript levels of genes identified in (a) were significantly upregulated after Arabidopsis exudate treatment. RNA was extracted from F. oryzae hypha and spores at 7 days after cultivation with or without the addition of Arabidopsis (At) exudate, and the transcript levels were determined by quantitative RT-PCR.…”

Microbiological Insights into the Stress-Alleviating Property of an Endophytic Bacillus altitudinis WR10 in Wheat under Low-Phosphorus and High-Salinity Stresses

“…It was revealed that IAA delays seed germination in wheat, and its exogenous application suppresses seed germination under high salinity in Arabidopsis [33,34]. However, a recent study showed that IAA levels are negatively related to the adverse effect of NaCl stress on wheat, suggesting that PGPB-produced IAA may be helpful for alleviating stress [35]. Many PGPB produces IAA, but the real effect of IAA on wheat seed germination under salinity stress is still unconfirmed.…”