Evolution of Phosphate Metabolism and the Adaptation of Tibetan Wild
Barley to Aluminum Stress
Abstract
Aluminum (Al) toxicity in acid soils significantly affects plant growth,
agricultural productivity and ecosystem health. Here we investigated
plant Al tolerance from evolutionary physiological, molecular, and
ecological perspectives. Genetic similarity and phylogenetic analysis of
Al tolerance-associated gene families showed that many of these were
conserved from streptophyte algae to angiosperms, indicating land plants
have evolved gradually in adaptation to Al-rich acid soil during plant
terrestrialization. In particular, vacuolar phosphate transporter
SPX-major facility superfamily (SPX-MFS) and inorganic phosphate (Pi)
transporter 1 subfamily (PHT1s) of streptophyte algae showed higher
genetic similarity to land plants than chlorophyte algae. PHT1 subfamily
exhibited a significant expand during the evolution from streptophyte
algae to liverworts and then to eudicots. Moreover, we identified an
Al-tolerant Tibetan wild barley accession XZ29, showing high levels of
Phosphorus(P)-containing glycolytic intermediates under Al stress. We
found a new Al-tolerance mechanism that Al-induced Pi efflux from root
elongation zone to chelate rhizosphere Al3+ and immobilization of Al
with P reduce Al accumulation in barley root cells. These results
indicated that Tibetan wild barley has evolved unique P transport and
metabolism for the adaptation to harsh conditions in eastern and
southeastern Tibet where acid soils contain high P.