Transgenic barley (Hordeum vulgare L.) expressing the wheat aluminium resistance gene (TaALMT1) shows enhanced phosphorus nutrition and grain production when grown on an acid soil

Abstract

SummaryBarley ( Hordeum vulgare L.), genetically modified with the Al 3+ resistance gene of wheat ( TaALMT1 ), was compared with a non-transformed sibling line when grown on an acidic and highly phosphate-fixing ferrosol supplied with a range of phosphorus concentrations.In short-term pot trials (26 days), transgenic barley expressing TaALMT1 (GP-ALMT1) was more efficient than a non-transformed sibling line (GP) at taking up phosphorus on acid soil, but the genotypes did not differ when the soil was limed. Differences in phosphorus uptake efficiency on acid soil could be attributed not only to the differential effects of aluminium toxicity on root growth between the genotypes, but also to differences in phosphorus uptake per unit root length. Although GP-ALMT1 out-performed GP on acid soil, it was still not as efficient at taking up phosphorus as plants grown on limed soil. GP-ALMT1 plants grown in acid soil possessed substantially smaller rhizosheaths than those grown in limed soil, suggesting that root hairs were shorter. This is a probable reason for the lower phosphorus uptake efficiency. When grown to maturity in large pots, GP-ALMT1 plants produced more than twice the grain as GP plants grown on acid soil and 80% of the grain produced by limed controls. Expression of TaALMT1 in barley was not associated with a penalty in either total shoot or grain production in the absence of Al 3+ , with both genotypes showing equivalent yields in limed soil. These findings demonstrate that an important crop species can be genetically engineered to successfully increase grain production on an acid soil.

Genotypic variation in phosphorus acquisition from sparingly soluble P sources is related to root morphology and root exudates in Brassica napus

“…Second, the higher Al concentration resulting from soil acidification under the Al-P treatment might stimulate the release of organic acid anions and indirectly supplement the Al-P nutrition compared to the Fe-P treatment [31,32]. As has been reported previously [33][34][35], in the presence of external Al, Al-resistant species or genotypes exude a number of organic anions including citrate, malate, and oxalate, and the exudation of citrate might contribute to the detoxification of Al and to the increased phosphate availability in the rhizosphere in rapeseed [36].…”

Improving phosphorus use efficiency in agriculture: opportunities for breeding

“…In addition, there may be alternative mechanisms of action. In acid soils, organic acids may not necessarily improve P uptake directly, but they could also be effective by providing protection from Al toxicity to root growth in turn indirectly improving P uptake through a better developed root system (Delhaize et al 2009). Organic acid exudation will also affect microorganisms involved in nutrient mobilisation.…”

“…Tian et al 2012). An aluminium resistance gene ALMT1 from wheat was shown to confer improved P uptake when expressed in barley (Delhaize et al 2009), and an Arabidopsis AVP1 H ? -PPase increased salt/drought tolerance of tomato and rice by promoting Na ?…”

Low pH, Aluminum, and Phosphorus Coordinately Regulate Malate Exudation through GmALMT1 to Improve Soybean Adaptation to Acid Soils

“…Since that first study, ALMT genes involved in Al tolerance have been cloned and characterized in Arabidopsis (Hoekenga et al, 2006) and rape (Brassica napus; Ligaba et al, 2006). It has been shown that overexpression of ALMT genes not only enhanced malate exudation but also improved Al tolerance in transgenic plants (Delhaize et al, 2009). P deficiency is another major soil constraint to agricultural production, limiting crop yield in 30% to 40% of the arable lands in the world (Runge-Metzger, 1995).…”