Overexpression of BdMATE Gene Improves Aluminum Tolerance in Setaria viridis

Abstract

Acidic soils are distributed worldwide, predominantly in tropical and subtropical areas, reaching around 50% of the arable soil. This type of soil strongly reduces crop production, mainly because of the presence of aluminum, which has its solubility increased at low pH levels. A well-known physiological mechanism used by plants to cope with Al stress involves activation of membrane transporters responsible for organic acid anions secretion from the root apex to the rhizosphere, which chelate Al, preventing its absorption by roots. In sorghum, a membrane transporter gene belonging to multidrug and toxic compound extrusion (MATE) family was identified and characterized as an aluminum-activated citrate transporter gene responsible for Al tolerance in this crop. Setaria viridis is an emerging model for C4 species and it is an important model to validate some genes for further C4 crops transformation, such as sugarcane, maize, and wheat. In the present work, Setaria viridis was used as a model plant to overexpress a newly identified MATE gene from Brachypodium distachyon (BdMATE), closely related to SbMATE, for aluminum tolerance assays. Transgenic S. viridis plants overexpressing a BdMATE presented an improved Al tolerance phenotype, characterized by sustained root growth and exclusion of aluminum from the root apex in transgenic plants, as confirmed by hematoxylin assay. In addition, transgenic plants showed higher root citrate exudation into the rhizosphere, suggesting that Al tolerance improvement in these plants could be related to the chelation of the metal by the organic acid anion. These results suggest that BdMATE gene can be used to transform C4 crops of economic importance with improved aluminum tolerance.

Two citrate transporters coordinately regulate citrate secretion from rice bean root tip under aluminum stress

“…For example, while transgenic plants overexpressing HvAACT1 (Furukawa et al, 2007;Zhou, Delhaize, Zhou, & Ryan, 2013), SbMATE (Magalhaes et al, 2007;Zhou et al, 2014) or VuMATE2 ( Figure 5) displayed increased citrate efflux under Al stress, transgenic tomato plants overexpressing VuMATE1 showed constitutive citrate efflux and this efflux was inhibited by Al stress (Yang et al, 2011). Recently, a similar scenario has been found in Setaria viridis transgenic plants overexpressing a MATE gene from Brachypodium distachuon (Ribeiro et al, 2017). Interestingly, transgenic barley plants overexpressing Arabidopsis FRD3 (Ferric Reductase Deffictive3) displayed constitutive citrate efflux independent of extracellular Al (Zhou et al, 2014).…”

GsMATE encoding a multidrug and toxic compound extrusion transporter enhances aluminum tolerance in Arabidopsis thaliana

“…Since then, a number of MATE genes have been reported to be involved in the Al-induced secretion of citrate in herbaceous plants. These genes include AtMATE in Arabidopsis [ 6 , 17 ], TaMATE in wheat [ 18 ], ZmMATE1 in maize [ 19 ], ScFRDL1 in rye [ 20 ], HvAACT1 in wheat and barley [ 21 ], SbMATE in barley [ 22 ], BoMATE in Arabidopsis [ 23 ], OsFRDL2 in rice [ 24 ], FeMATE1 and FeMATE2 in buckwheat [ 17 ], BdMATE in Setaria viridis [ 25 ], and MtMATE66 in Medicago truncatula [ 26 ]. All these homologous genes encode MATE proteins that are required for external Al-resistance, and are primarily localized to the root epidermis cells [ 16 , 17 , 20 , 23 ].…”

Enhanced Aluminum Tolerance in Sugarcane: Evaluation of SbMATE Overexpression and Genome-wide Identification of ALMTs in Saccharum Spp.

“…The hematoxylin staining occurs by the complexation of the dye with Al. This assay is commonly used for rapid and qualitative screening of plants that may be tolerant to Al [3,13,15,16,17,19,20]. The root apex of plants demonstrating high accumulation of Al shows intense purple staining in the presence of hematoxylin.…”

“…In Brazil, for example, an alternative for the expansion of sugarcane planting area is the Cerrado region, a biome characterized by acidic soil. Therefore, a great effort has been made by the scienti c community to improve traits for sugarcane growth in poor and acid soils [3].…”

“…Previous studies have demonstrated that overexpression of a MATE gene conferred tolerance to Al via citrate exudation in the rhizosphere in plants such as Sorghum bicolor [9] and in Setaria viridis, a model plant for grasses closely related to sugarcane [3]. Based on these studies, transgenic sugarcane plants constitutively overexpressing the Sorghum bicolor MATE gene (SbMATE) were generated to verify if the transformed plants could be tolerant to aluminum when compared to non-transformed (NT) plants.…”