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Regulation of Plant Growth, Photosynthesis, Antioxidation and Osmosis by an Arbuscular Mycorrhizal Fungus in Watermelon Seedlings under Well-Watered and Drought Conditions.

Mo Y, Wang Y, Yang R, Zheng J, Liu C, Li H, Ma J, Zhang Y, Wei C, Zhang X - Front Plant Sci (2016)

Bottom Line: Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown.Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition.Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation.

View Article: PubMed Central - PubMed

Affiliation: College of Horticulture, Northwest A&F University Yangling, China.

ABSTRACT
Drought stress has become an increasingly serious environmental issue that influences the growth and production of watermelon. Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown. In this study, the effects of Glomus versiforme symbiosis on the growth, physio-biochemical attributes, and stress-responsive gene expressions of watermelon seedlings grown under well-watered and drought conditions were investigated. The results showed that AM colonization did not significantly influence the shoot growth of watermelon seedlings under well-watered conditions but did promote root development irrespective of water treatment. Drought stress decreased the leaf relative water content and chlorophyll concentration, but to a lesser extent in the AM plants. Compared with the non-mycorrhizal seedlings, mycorrhizal plants had higher non-photochemical quenching values, which reduced the chloroplast ultrastructural damage in the mesophyll cells and thus maintained higher photosynthetic efficiency. Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition. Consequently, AM plants exhibited lower accumulation of MDA, H2O2 and [Formula: see text] compared with non-mycorrhizal plants. Under drought stress, the soluble sugar and proline contents were significantly increased, and further enhancements were observed by pre-treating the drought-stressed plants with AM. Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation. This study contributes to advances in the knowledge of AM-induced drought tolerance.

No MeSH data available.


Related in: MedlinePlus

Relative expression levels of the RBCS(A), RBCL(B), PAO(C), PPH(D), Cu-Zn SOD(E), CAT(F), APX(G), GR(H), MDHAR(I), and DHAR(J) genes in mycorrhizal (+M) and non-mycorrhizal (-NM) watermelon seedlings grown under WW and DS conditions. The expression level of the genes in the non-mycorrhizal seedlings grown under WW conditions was used as the control with a nominal value of 1. T-test was performed to compare differences between inoculation treatments under the same water treatment. Different letters following the values indicate significant differences between treatments at P < 0.05. Two-way ANOVA output: ns, not significant; ∗P < 0.05, ∗∗P < 0.01. Data represent the means ± SD of three replicates.
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Figure 6: Relative expression levels of the RBCS(A), RBCL(B), PAO(C), PPH(D), Cu-Zn SOD(E), CAT(F), APX(G), GR(H), MDHAR(I), and DHAR(J) genes in mycorrhizal (+M) and non-mycorrhizal (-NM) watermelon seedlings grown under WW and DS conditions. The expression level of the genes in the non-mycorrhizal seedlings grown under WW conditions was used as the control with a nominal value of 1. T-test was performed to compare differences between inoculation treatments under the same water treatment. Different letters following the values indicate significant differences between treatments at P < 0.05. Two-way ANOVA output: ns, not significant; ∗P < 0.05, ∗∗P < 0.01. Data represent the means ± SD of three replicates.

Mentions: To gain further insights into the molecular regulation of watermelon seedlings in the presence of AM colonization, a subset of stress-responsive genes involved in photosynthesis (RBCL and RBCS), chlorophyll degradation (PAO and PPH) and the antioxidant response (Cu-Zn SOD, CAT, APX, GR, MDHAR, and DHAR) were analyzed using qRT-PCR. The results indicated that mycorrhizal inoculation significantly increased the gene expression of RBCL and RBCS regardless of treatment (Figures 6A,B). Compared with the well-watered control, drought stress inhibited the expression of RBCS and RBCS in watermelon plants, but with less effect on the the mycorrhizal seedlings. PAO and PPH were highly up-regulated by the drought treatment, i.e., by 3.19- and 8.28-fold in the non-mycorrhizal plants, and 2.02- and 2.81-fold, respectively, in the mycorrhizal plants (Figures 6C,D). Drought stress also enhanced the antioxidant gene expression; a greater enhancement was observed in the inoculated than in the non-inoculated plants (Figures 6E–J). The expression levels of Cu-Zn SOD, CAT, APX, GR, MDHAR, and DHAR in the DS+M plants were 1.75-, 1.93-, 1.76-, 1.85-, 2.01-, and 2.18-fold higher, respectively, than in the DS-NM plants. Interactions between watering and AM inoculation were significant for expressions of all examined genes except RBCL (P < 0.05).


Regulation of Plant Growth, Photosynthesis, Antioxidation and Osmosis by an Arbuscular Mycorrhizal Fungus in Watermelon Seedlings under Well-Watered and Drought Conditions.

Mo Y, Wang Y, Yang R, Zheng J, Liu C, Li H, Ma J, Zhang Y, Wei C, Zhang X - Front Plant Sci (2016)

Relative expression levels of the RBCS(A), RBCL(B), PAO(C), PPH(D), Cu-Zn SOD(E), CAT(F), APX(G), GR(H), MDHAR(I), and DHAR(J) genes in mycorrhizal (+M) and non-mycorrhizal (-NM) watermelon seedlings grown under WW and DS conditions. The expression level of the genes in the non-mycorrhizal seedlings grown under WW conditions was used as the control with a nominal value of 1. T-test was performed to compare differences between inoculation treatments under the same water treatment. Different letters following the values indicate significant differences between treatments at P < 0.05. Two-way ANOVA output: ns, not significant; ∗P < 0.05, ∗∗P < 0.01. Data represent the means ± SD of three replicates.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4862978&req=5

Figure 6: Relative expression levels of the RBCS(A), RBCL(B), PAO(C), PPH(D), Cu-Zn SOD(E), CAT(F), APX(G), GR(H), MDHAR(I), and DHAR(J) genes in mycorrhizal (+M) and non-mycorrhizal (-NM) watermelon seedlings grown under WW and DS conditions. The expression level of the genes in the non-mycorrhizal seedlings grown under WW conditions was used as the control with a nominal value of 1. T-test was performed to compare differences between inoculation treatments under the same water treatment. Different letters following the values indicate significant differences between treatments at P < 0.05. Two-way ANOVA output: ns, not significant; ∗P < 0.05, ∗∗P < 0.01. Data represent the means ± SD of three replicates.
Mentions: To gain further insights into the molecular regulation of watermelon seedlings in the presence of AM colonization, a subset of stress-responsive genes involved in photosynthesis (RBCL and RBCS), chlorophyll degradation (PAO and PPH) and the antioxidant response (Cu-Zn SOD, CAT, APX, GR, MDHAR, and DHAR) were analyzed using qRT-PCR. The results indicated that mycorrhizal inoculation significantly increased the gene expression of RBCL and RBCS regardless of treatment (Figures 6A,B). Compared with the well-watered control, drought stress inhibited the expression of RBCS and RBCS in watermelon plants, but with less effect on the the mycorrhizal seedlings. PAO and PPH were highly up-regulated by the drought treatment, i.e., by 3.19- and 8.28-fold in the non-mycorrhizal plants, and 2.02- and 2.81-fold, respectively, in the mycorrhizal plants (Figures 6C,D). Drought stress also enhanced the antioxidant gene expression; a greater enhancement was observed in the inoculated than in the non-inoculated plants (Figures 6E–J). The expression levels of Cu-Zn SOD, CAT, APX, GR, MDHAR, and DHAR in the DS+M plants were 1.75-, 1.93-, 1.76-, 1.85-, 2.01-, and 2.18-fold higher, respectively, than in the DS-NM plants. Interactions between watering and AM inoculation were significant for expressions of all examined genes except RBCL (P < 0.05).

Bottom Line: Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown.Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition.Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation.

View Article: PubMed Central - PubMed

Affiliation: College of Horticulture, Northwest A&F University Yangling, China.

ABSTRACT
Drought stress has become an increasingly serious environmental issue that influences the growth and production of watermelon. Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown. In this study, the effects of Glomus versiforme symbiosis on the growth, physio-biochemical attributes, and stress-responsive gene expressions of watermelon seedlings grown under well-watered and drought conditions were investigated. The results showed that AM colonization did not significantly influence the shoot growth of watermelon seedlings under well-watered conditions but did promote root development irrespective of water treatment. Drought stress decreased the leaf relative water content and chlorophyll concentration, but to a lesser extent in the AM plants. Compared with the non-mycorrhizal seedlings, mycorrhizal plants had higher non-photochemical quenching values, which reduced the chloroplast ultrastructural damage in the mesophyll cells and thus maintained higher photosynthetic efficiency. Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition. Consequently, AM plants exhibited lower accumulation of MDA, H2O2 and [Formula: see text] compared with non-mycorrhizal plants. Under drought stress, the soluble sugar and proline contents were significantly increased, and further enhancements were observed by pre-treating the drought-stressed plants with AM. Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation. This study contributes to advances in the knowledge of AM-induced drought tolerance.

No MeSH data available.


Related in: MedlinePlus