2012 Annual Report
1a.Objectives (from AD-416):
The objectives of this cooperative research project are to increase our understanding of mechanisms of aluminum tolerance, heavy metal transport, and nutritional quality and health-promoting properties of plants.
1b.Approach (from AD-416):
1) A combination of joint-association mapping, comparative genomics, and biochemistry approaches will be used to study aluminum tolerance genes we recently cloned in wheat, sorghum and maize from the ALMT and MATE gene families. The research on sorghum and maize involves collaborative research with Embrapa Maize and Sorghum in Sete Lagoas, Brazil. The research on rice involves collaborative research with South China Agricultural University, Guangzhou, China, and Zhejiang University, Huangzhou, China. The information will be used to enhance acid soil tolerance of cereal crops, with a focus on sorghum, maize and rice. .
2)The molecular physiology of heavy metal transport will be studied in the heavy metal hyperaccumulator, Thlaspi caerulescens. We have identified a number of genes that are candidates for involvement in metal hyperaccumulation in Thlaspi and will study them in more detail to determine if they are indeed, hyperaccumulation genes. These will be used via biotechnology to improve plants for use in remediation of metal-contaminated soils. .
3)Recently identified QTL that enhance Fe bioavailability in maize seed will be characterized and a combined genomic, genetic and metabolic approach will be employed to identify the genes underlying the QTL as well as the secondary compounds underlying the FE bioavailability.
Progress for this project in 2012 involved continued research sorghum and rice aluminum tolerance, which is an important agronomic trait for crops grown on acid soils that are prevalent in the US and the rest of the world, especially in developing countries. On acid soils, Al ions are dissolved into the soil solution and are toxic to and damage plant roots, thus greatly reducing crop vigor and yields. This research is based on our previous discovery of the major sorghum gene (SbMATE) that controls most of the tolerance to aluminum (Al) toxicity in sorghum. We have identified a novel protein that binds to and regulates SbMATE making it very efficient at the release of citrate acid, which SbMATE transports out of roots into the soil where it binds to and detoxifies Al ions. We call this protein SbMBP, for Sorghum bicolor MATE binding protein.
In rice, we showed that a protein from the Nramp family of metal transporters called Nrat1 (for Nramp aluminum transporter.
1)mediates the uptake of Al ions from the cell wall into the root tip cells, where the Al is then stored in an internal compartment and detoxified. This lowers the level of Al in the cell wall which helps protect the cell wall from Al toxicity. Both SbMBP and Nrat1 are part of our growing molecular toolbox of genes/proteins that can be used via molecular breeding approaches to improve sorghum and rice Al tolerance.