Enhanced Drought Stress Tolerance by the Arbuscular Mycorrhizal Symbiosis in a Drought-Sensitive Maize Cultivar Is Related to a Broader and Differential Regulation of Host Plant Aquaporins than in a Drought-Tolerant Cultivar

Abstract

The arbuscular mycorrhizal (AM) symbiosis has been shown to improve maize tolerance to different drought stress scenarios by regulating a wide range of host plants aquaporins. The objective of this study was to highlight the differences in aquaporin regulation by comparing the effects of the AM symbiosis on root aquaporin gene expression and plant physiology in two maize cultivars with contrasting drought sensitivity. This information would help to identify key aquaporin genes involved in the enhanced drought tolerance by the AM symbiosis. Results showed that when plants were subjected to drought stress the AM symbiosis induced a higher improvement of physiological parameters in drought-sensitive plants than in drought-tolerant plants. These include efficiency of photosystem II, membrane stability, accumulation of soluble sugars and plant biomass production. Thus, drought-sensitive plants obtained higher physiological benefit from the AM symbiosis. In addition, the genes ZmPIP1;1, ZmPIP1;3, ZmPIP1;4, ZmPIP1;6, ZmPIP2;2, ZmPIP2;4, ZmTIP1;1, and ZmTIP2;3 were down-regulated by the AM symbiosis in the drought-sensitive cultivar and only ZmTIP4;1 was up-regulated. In contrast, in the drought-tolerant cultivar only three of the studied aquaporin genes (ZmPIP1;6, ZmPIP2;2, and ZmTIP4;1) were regulated by the AM symbiosis, resulting induced. Results in the drought-sensitive cultivar are in line with the hypothesis that down-regulation of aquaporins under water deprivation could be a way to minimize water loss, and the AM symbiosis could be helping the plant in this regulation. Indeed, during drought stress episodes, water conservation is critical for plant survival and productivity, and is achieved by an efficient uptake and stringently regulated water loss, in which aquaporins participate. Moreover, the broader and contrasting regulation of these aquaporins by the AM symbiosis in the drought-sensitive than the drought-tolerant cultivar suggests a role of these aquaporins in water homeostasis or in the transport of other solutes of physiological importance in both cultivars under drought stress conditions, which may be important for the AM-induced tolerance to drought stress.

Effect of triple superphosphate and biowaste compost on mycorrhizal colonization and enzymatic P mobilization under maize in a long‐term field experiment

“…Significantly higher mycorrhizal colonization in the control than after TSP application in 2016 (Fig. ) might have enhanced the drought tolerance of maize in the control, since this impact of mycorrhizal symbiosis in maize was described in advance by Quiroga et al () for drought‐sensitive cultivars. Decreased mycorrhizal colonization was particularly observed after TSP application without organic amendments (see Fig.…”

The arbuscular mycorrhizal symbiosis regulates aquaporins activity and improves root cell water permeability in maize plants subjected to water stress

“…We analysed the mRNA levels of ZmPIP1;1 , ZmPIP1;3 , ZmPIP2;2 , ZmPIP2;4 , ZmTIP1;1 , ZmTIP2;3 , ZmTIP4;1 , and ZmNIP2;1 genes, previously selected as being regulated by the AM symbiosis (Quiroga et al, ), as well as other aquaporins recognized for their role in root water transport ( ZmPIP2;1 , ZmPIP2;5 , and ZmPIP2;6 ; Figure a). Several of the analysed aquaporins did not show significant differences in their expression patterns.…”

“…The efficiency of photosystem II of light‐adapted maize leaves was measured with Fluor‐Pen FP100 (Photon Systems Instruments, Brno, Czech Republic) as previously described in Quiroga et al (, ) in the second youngest leaf of 10 different plants of each treatment after 8 weeks of growth.…”

“…Thus, to keep the stomata open, the root water conductivity (L pr ) must be high enough (Sack & Holbrook, ). The AM association has been found to differently regulate root water transport both under well‐watered and water deficit conditions, generally enhancing L pr (Aroca, Porcel, & Ruiz‐lozano, ; Bárzana et al, ; Bárzana, Aroca, Bienert, Chaumont, & Ruiz‐Lozano, ; Bárzana, Aroca, & Ruiz‐Lozano, ; Quiroga, Erice, Aroca, Chaumont, & Ruiz‐Lozano, ; Sánchez‐Romera, Ruiz‐Lozano, Zamarreño, García‐Mina, & Aroca, ). This effect has been related to the uptake of water through fungal hyphae from soil pores inaccessible to roots and to changes induced by the AM fungi affecting the hydraulic properties of the soil (Allen, ; Augé et al, ; Hallet et al, ) and inside the roots (Ruiz‐Lozano & Aroca, ).…”

Growth and nutrition of cowpea (Vigna unguiculata) under water deficit as influenced by microbial inoculation via seed coating

“…Besides their contribution to nutrient acquisition and biocontrol, PGPR can also confer drought tolerance in plants by osmotic adjustment, antioxidant metabolisms and phytohormone modulation (Rubin, van Groenigen, & Hungate, ; Vurukonda et al., ). AM fungal symbiosis can improve plant antioxidant activity, osmotic regulation, photosynthetic rates and pigments, root water absorption and transport and uptake of nutrients, especially phosphorus (P) (Li et al., ; Oliveira, Rocha, Ma, Vosátka, & Freitas, ; Oliveira, Ma et al., ; Quiroga, Erice, Aroca, Chaumont, & Ruiz‐Lozano, ).…”