Molecular mapping of a gene responsible for Al-activated secretion of citrate in barley

Abstract

Aluminium (Al) toxicity is an important limitation to barley (Hordeum vulgare L.) on acid soil. Al-resistant cultivars of barley detoxify Al externally by secreting citrate from the roots. To link the genetics and physiology of Al resistance in barley, genes controlling Al resistance and Al-activated secretion of citrate were mapped. An analysis of Al-induced root growth inhibition from 100 F2 seedlings derived from an Al-resistant cultivar (Murasakimochi) and an Al-sensitive cultivar (Morex) showed that a gene associated with Al resistance is localized on chromosome 4H, tightly linked to microsatellite marker Bmag353. Quantitative trait locus (QTL) analysis from 59 F4 seedlings derived from an F3 plant heterozygous at the region of Al resistance on chromosome 4H showed that a gene responsible for the Al-activated secretion of citrate was also tightly linked to microsatellite marker Bmag353. This QTL explained more than 50% of the phenotypic variation in citrate secretion in this population. These results indicate that the gene controlling Al resistance on barley chromosome 4H is identical to that for Al-activated secretion of citrate and that the secretion of citrate is one of the mechanisms of Al resistance in barley. The identification of the microsatellite marker associated with both Al resistance and citrate secretion provides a valuable tool for marker-assisted selection of Al-resistant lines.

The roles of organic anion permeases in aluminium resistance and mineral nutrition

“…The recent report of an ALMT sequence located on barley chromosome 4H appears consistent with conserved gene function between wheat and barley [20]. However, the mechanism encoded at 4HL in barley involves the Al 3+ -activated efflux of citrate and not malate [33]. This observation implies that either an ALMT gene encodes the Al 3+ -activated citrate transporter or that the chromosomal location is co-incidental such that the Al 3+ resistance gene encodes a different protein, for example a MATE, which preferentially transports citrate.…”

“…It is notable that the four ALMT proteins characterised to date specifically transport malate whereas the MATE proteins described here from sorghum and Arabidopsis transport citrate. An Al 3+ resistance gene in barley maps to chromosome 4HL at an apparently orthologous locus to that of TaALMT1 on chromosome 4DL in wheat [33,43]. The recent report of an ALMT sequence located on barley chromosome 4H appears consistent with conserved gene function between wheat and barley [20].…”

“…Although barley is relatively sensitive to Al 3+ toxicity some variation in resistance is present among genotypes. Like sorghum, Al 3+ resistance in barley is correlated with citrate efflux, a phenotype controlled by the Alp locus on chromosome 4H [33]. Recent work has exploited the synteny between the rice and barley genomes to identify a gene encoding a MATE within the Alp locus (H. Raman, personal communication).…”

Molecular diversity and genetic relationships in Secale

“…Vavilov 1926;Stutz 1972), cytogenetic (Khush 1962;Cuadrado and Jouve 2002;Zhou et al 2010), chemotaxonomic (Dedio et al 1969), biochemical, like isozymes (Vences et al 1987;Matos et al 2001); and molecular methods such as amplified fragment length polymorphism (AFLP) (Chikmawati et al 2005(Chikmawati et al , 2012, ISSR (Matos et al 2001;Ren et al 2011), random amplified polymorphic DNA (RAPD) (Matos et al 2001;Ma et al 2004), restriction fragment length polymorphism (RFLP) (Loarce et al 1996), simple sequence repeat (SSR) (Shang et al 2006;Jenabi et al 2011) and ribosomal DNA studies (De Bustos and Jouve 2002).…”

Review Genetic and molecular mechanisms of aluminum tolerance in plants

“…As in sorghum, Al tolerance in barley is related to citrate efflux mediated by HvAACT1, which also belongs to the MATE family and is highly expressed in roots of Al-tolerant barley genotypes (Furukawa et al, 2007). QTL mapping in this species has shown that HvAACT1 is located on chromosome 4H, co-localizing with a major QTL that explains more than 50% of the phenotypic variation in Al-activated citrate exudation (Ma et al, 2004b).…”