Aluminum tolerance mechanisms in Kenyan maize germplasm are independent from the citrate transporter ZmMATE1

Abstract

Aluminum (Al) toxicity on acid soils adversely affects maize yields, which can be overcome by combining soil amendments with genetic tolerance. In maize, ZmMATE1 confers Al tolerance via Al-activated citrate release, whereby citrate forms non-toxic complexes with Al3+ in the rhizosphere. Here, we investigated Al tolerance mechanisms in maize germplasm originated from Kenya based on quantitative trait loci (QTL) mapping. Five QTLs and four epistatic interactions explained ~51% of the phenotypic variation for Al tolerance. The lack of Al tolerance QTL on chromosome 6 and the much lower expression of ZmMATE1 in both Kenyan lines than in Cateto Al237, which donates the superior allele of ZmMATE1, strongly indicate that this gene does not play a significant role in Al tolerance in neither parent. In turn, maize homologs to genes previously implicated in Al tolerance in other species, ZmNrat1, ZmMATE3, ZmWRKY and ZmART1, co-localized with Al tolerance QTL and were more highly expressed in the parent that donate favorable QTL alleles. However, these candidate genes will require further studies for functional validation on maize Al tolerance. The existence of Al tolerance mechanisms independent from ZmMATE1 suggests it is possible to develop highly Al tolerant cultivars by pyramiding complementary Al tolerance genes in maize.

Aluminum or Low pH – Which Is the Bigger Enemy of Barley? Transcriptome Analysis of Barley Root Meristem Under Al and Low pH Stress

“…Three metal transporters, specifically upregulated only by Al, encode NRAMP proteins (Natural Resistance-Associated Macrophage Protein). One of them, HORVU.MOREX.r2.7HG0610240 (log 2 FC = 1.35) is homologous to ZmNrat1 ( nramp Aluminum Transporter 1 ) that is known to be a membrane transporter of aluminum in maize ( Guimaraes et al, 2014 ; Matonyei et al, 2020 ). Similar to the barley gene, ZmNrat1 was also upregulated by Al treatment.…”

Genotypic differences in aluminum tolerance of cowpea accessions utilizing germination parameters

“…Target improvement for aluminum tolerance will depend on existence of sufficient genetic variability and identification of traits that are correlated under stress. Findings from many workers suggest that many approaches could be adopted in breeding for aluminum tolerance and identification of germane traits should be the focus of each breeding program [10,28,32,42]. In this study, percentage germination was positively correlated with number of roots, hypocotyl length and fresh weight of shoot.…”

“…Acid soils occupy nearly 17 million hectares in Nigeria, making up 18% of the total land area [8], and about 35% of the world's arable land [9], and about 50% of the possible cultivated land [4,10,11,12]. Soils of the humid tropics, especially the whole lands of the South Eastern Nigeria are acidic [13,14,15], due to high precipitations (1500 mm and above) in these regions which lead to the leaching of substantial amounts of exchangeable bases from soil surfaces [16].…”

“…Since there is a direct correlation between soil acidity and aluminum toxicity, liming of the soil could be adopted to raise the pH level to enhance plant growth and development under aluminum stress [17]. However, the practice of agriculture in developing countries has been mainly relegated to subsistence levels, hence it is unwise both economically and logistically to adopt liming of soil by the resource poor farmers [10,16,18]. Excess liming also have negative consequences, such as leaching of soil minerals causing Manganese (Mn) deficiencies in soils as well as acquisition by plants and Phosphorus (P) deficiencies in soils [18].…”

Sequencing and gene expression studies for Al tolerance in contrasting genotypes of tropical maize

“…The superior tolerance of V 18 may reflect the presence of more effective tolerance genes since this genotype comes from agricultural regions of low technological level, characterized by environments with low natural fertility and high Al saturation (Coelho et al 2016). Maron et al (2010), Guimarães et al (2014), Matonyei et al (2017), and Matonyei et al (2020) revealed that this genomic region (ZmMATE1) explains most of the phenotypic variation of Al tolerance in Cateto maize. The greater tolerance observed in the germplasm of landrace maize in the present study could also be directly related to the presence of the same genes coming from the Cateto breed of maize, a germplasm that is very common in the region these landrace varieties of maize were collected (Coelho et al 2018).…”