| Plant root system is one of the most important agronomic traits. The ability to developgood root system has great significance for its adaptability to the environmental stress andability to survive. The morphological structure of the root system is in fact a “sensory system”.The way root systems develop is affected by a diversity of biological and abiotic factors andthe root systems can show high plasticity. Therefore, it is of vital significance to research onthe plasticity of the plant root system, for it contributes to the efficiency of nutrients and wateruptake. Recent years, some breakthrough has been made on the molecular mechanism studyof the plasticity of the plant root development, whereas little is known about the geneticfactors and signal transduction approach. For this reason, our research team has selected someroot development related mutants and identified the corresponding mutant genes to furtherstudy the growth and development mechanism of the root system morphogenesis.The abnormal root hair mutants used in this experiment are provided by the researchteam. The mutant is treated with0.3%EMS and is selected. It is named as rhm, because themutant is characterized of multiple root hair.A series of phenotypic identification of the rhm was made and the results are comparedto that of the wt (Wild Type col0) so as to observe the difference of rhm growth anddevelopment. The result shows that during the vegetative growth period, the plant isabnormally small, late bolting, about10days late. The length of fruits is only70%of the wt.The number of seeds is only half that of the wt. Under the penetrating and stress treatment ofsugar, sodium salt, mannitol and salicylic, the major root growth of the mutant rhm issuppressed. Particularly under the treatment of100mM NaCl, the extension of wt major rootis20times that of the mutant. The growth of the major root extension is suppressed. Underthe treatment of250mM Man, the extension of wt major root is6times that of the mutant.Under the oxidative stress of hydrogen peroxide, the amount of lateral roots andadventitious roots of the mutant decreases. Meanwhile, seed germination presents differentphenotypic features, under the treatment of ABA, mannitol and NaCl and is sensitive toABA and insensitive to mannitol and NaCl.It is verified by the genetic experiment that this mutant is a single recessive geneticmutant. By means of the map-based cloning technology, the mutation site is located on the lower part of the fourth chromosome, which is F19F18BAC. Sequencing analysis shows thatthe1136thbase at the Short Root Gene has changed from G to A. The protein sequencinganalysis shows that GAA has changed to AAA, thus changing from Glutamic to lysine.Therefore it can be predicted that the mutation of this base causes the change of Glutamicsequence and consequently the mutation of the protein. This leads to a series of physiologicaland biochemical changes of the plants, including the abnormal development of the root hairmutant (rhm) and other abnormal phenotypic development.Previous study has shown that SHR is involved in root morphogenesis. The short root(SHR) gene is a key regulator not only in root radial patterning but also in root meristemmaintenance. Currently, SHR is characterized as both a transcription factor for activatingdownstream gene expression and a short-range signal for modulating root development. Dueto the complicity of the regulation network, the signal pathway is still not clear.There have been many reports on SHR genes. However, the research on rhm mutantsmay further enrich the study of SHR genes as well as that of the regulation networks of rootsystem morphogenesis. Specific regulation mechanism requires further research. |
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