摘要
Salinity is an abiotic stress that substantially limits crop production worldwide. To identify salt stress tolerance determinants, we screened for Arabidopsis mutants that are hypersensitive to salt stress and designated these mutants as short root in salt medium （rsa）. One of these mutants, rsa3-1, is hypersensitive to NaCI and LiCI but not to CsCI or to general osmotic stress. Reactive oxygen species （ROS） over-accumulate in rsa3-1 plants under salt stress. Gene expression profiling with Affymetrix microarray analysis revealed that RSA3 controls expression of many genes including genes encoding proteins for ROS detoxification under salt stress. Map-based cloning showed that RSA3 encodes a xyloglucan galactosyltransferase, which is allelic to a gene previously named MUR3/KAM1. The RSA3/ MUR3/KAMl-encoded xylogluscan galactosyltransferase regulates actin microfilament organization （and thereby con- tributes to endomembrane distribution） and is also involved in cell wall biosynthesis. In rsa3-1, actin cannot assemble and form bundles as it does in the wild-type but instead aggregates in the cytoplasm. Furthermore, addition of phal- Ioidin, which prevents actin depolymerization, can rescue salt hypersensitivity of rsa3-1. Together, these results sug- gest that RSA3/MUR3/KAM1 along with other cell wall-associated proteins plays a critical role in salt stress tolerance by maintaining the proper organization of actin microfilaments in order to minimize damage caused by excessive ROS.
Salinity is an abiotic stress that substantially limits crop production worldwide. To identify salt stress tolerance determinants, we screened for Arabidopsis mutants that are hypersensitive to salt stress and designated these mutants as short root in salt medium （rsa）. One of these mutants, rsa3-1, is hypersensitive to NaCI and LiCI but not to CsCI or to general osmotic stress. Reactive oxygen species （ROS） over-accumulate in rsa3-1 plants under salt stress. Gene expression profiling with Affymetrix microarray analysis revealed that RSA3 controls expression of many genes including genes encoding proteins for ROS detoxification under salt stress. Map-based cloning showed that RSA3 encodes a xyloglucan galactosyltransferase, which is allelic to a gene previously named MUR3/KAM1. The RSA3/ MUR3/KAMl-encoded xylogluscan galactosyltransferase regulates actin microfilament organization （and thereby con- tributes to endomembrane distribution） and is also involved in cell wall biosynthesis. In rsa3-1, actin cannot assemble and form bundles as it does in the wild-type but instead aggregates in the cytoplasm. Furthermore, addition of phal- Ioidin, which prevents actin depolymerization, can rescue salt hypersensitivity of rsa3-1. Together, these results sug- gest that RSA3/MUR3/KAM1 along with other cell wall-associated proteins plays a critical role in salt stress tolerance by maintaining the proper organization of actin microfilaments in order to minimize damage caused by excessive ROS.
基金
National Science Foundation (NSF) grants IOS0919745 and MCB0950242 to J.Z.and by NSF grant DB10922650
