Root-hair growth and development regulated by soil microbes is associated with auxin. In this background, we hypothesized that mycorrhizal fungal inoculation induces greater root-hair growth through stimulated auxin synthesis and transport under water stress conditions. Trifoliate orange (Poncirus trifoliata) was inoculated with an arbuscular mycorrhizal (AM) fungus (Funneliformis mosseae) under well-watered (WW) and drought stress (DS) for 9 weeks. Compared with non-AM seedlings, AM seedlings displayed significantly higher density, length, and diameter of root hairs and root indoleacetic acid (IAA) level, whereas lower total root IAA efflux, regardless of soil moisture status. Root PtYUC3 and PtYUC8 involved in IAA biosynthesis were up-regulated by mycorrhization under WW and DS, whereas AM-modulated expression in PtTAA1, PtTAR2, PtYUC4, and PtYUC6 depended on status of soil moisture. Mycorrhizal inoculation down-regulated the transcript level of root auxin efflux carriers like PtPIN1 and PtPIN3, whereas significantly up-regulated the expression of root auxin-species influx carriers like PtABCB19 and PtLAX2 under DS. These results indicated that AMF-stimulated greater root-hair growth of trifoliate orange under DS that is independent on AMF species is related with mycorrhiza-modulated auxin synthesis and transport, which benefits the host plant to enhance drought tolerance.

• MeSH
• Biological Transport MeSH
• Stress, Physiological * MeSH
• Glomeromycota growth & development   physiology   MeSH
• Indoleacetic Acids metabolism   MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Mycorrhizae growth & development   physiology   MeSH
• Droughts * MeSH
• Colony Count, Microbial MeSH
• Poncirus genetics   growth & development   microbiology   physiology   MeSH
• Gene Expression Regulation, Plant MeSH
• Genes, Plant MeSH
• Plant Proteins genetics   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• indoleacetic acid MeSH Browser
• Indoleacetic Acids MeSH
• RNA, Messenger MeSH
• Plant Proteins MeSH

Plant roots are the first parts of plants to face drought stress (DS), and thus root modification is important for plants to adapt to drought. We hypothesized that the roots of arbuscular mycorrhizal (AM) plants exhibit better adaptation in terms of morphology and phytohormones under DS. Trifoliate orange seedlings inoculated with Diversispora versiformis were subjected to well-watered (WW) and DS conditions for 6 weeks. AM seedlings exhibited better growth performance and significantly greater number of 1st, 2nd, and 3rd order lateral roots, root length, area, average diameter, volume, tips, forks, and crossings than non-AM seedlings under both WW and DS conditions. AM fungal inoculation considerably increased root hair density under both WW and DS and root hair length under DS, while dramatically decreased root hair length under WW but there was no change in root hair diameter. AM plants had greater concentrations of indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin in roots, which were significantly correlated with changes in root morphology. These results support the hypothesis that AM plants show superior adaptation in root morphology under DS that is potentially associated with indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin levels.

• MeSH
• Acetates metabolism   MeSH
• Cyclopentanes metabolism   MeSH
• Adaptation, Physiological MeSH
• Glomeromycota metabolism   physiology   MeSH
• Calmodulin metabolism   MeSH
• Plant Roots growth & development   microbiology   MeSH
• Indoleacetic Acids metabolism   MeSH
• Mycorrhizae growth & development   MeSH
• Droughts MeSH
• Nitric Oxide metabolism   MeSH
• Oxylipins metabolism   MeSH
• Poncirus growth & development   microbiology   MeSH
• Plant Growth Regulators metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acetates MeSH
• Cyclopentanes MeSH
• indoleacetic acid MeSH Browser
• Calmodulin MeSH
• Indoleacetic Acids MeSH
• methyl jasmonate MeSH Browser
• Nitric Oxide MeSH
• Oxylipins MeSH
• Plant Growth Regulators MeSH