Regulated Mechanism Of EXPA7 Subclade Members On Rice Root Hair Elongation

Root hair is an important organ for plants to uptake nutrients and water from the rhizosphere and serves as a site of interaction with soil microorganisms. Root hair development can be divided into three stages:cell specification, initiation, and elongation. Extensive studies have been reported on root hair development in Arabidopsis (the dicot model plant). In rice (the monocot model plant) the knowledge on root hair development is still limited.It has been reported in Arabidopsis that AtEXPA7 and AtEXPA18 are tightly linked to root hair initiation and development. But the homozygous T-DNA insert mutant of AtEXPA7 has no obvious compaired phenotype with the wild type in root hair, for which the functional redundancy by AtEXPA18 and perhaps other expansin genes.A short root hair mutant caused by mutation of OsEXPA17, is a orthology gene of AtEXPA7, has been founded. RNA interference of OsEXPA17 gene also results in short root hair phenotype, which conforms that the point mutant of OsEXPA17 makes the gene function lost. The point mutation results in a change of 104th site amino acid Gly to Arg. There are two cysteines in 103th site and 106th site near 104th site which can form two disulfide linkage with 74th site and 180th site cysteines alternatively. So we presume the amino acid change in 104th site may influence the disulfide linkage structure.Overexpressing OsEXPA30 and AtEXPA7 can partially restore OsexpA17 short root hair mutant.Through transient expression of OsEXPA17, OsEXPA30 and OsexpA17, we discover that they are plasma membrane proteins through plasmolysis.