The Studies Of SPIKE1 Gene Regulatory Mechanism During Trichome Development In Arabidopsis

Trichome is divided by the epidermal tissues of the ground parts of the plant.It has various forms and a wide range of biological functions.The development of trichomes is regulated by the genetic and environmental factors.In order to further dissect genetic interactions during the development of trichomes,we carried out exhaustive screens for additional Arabidopsis mutants with altered trichome morphology.This thesis reported the isolation of a mutant with aberrantly branched trichome,abt1-1(spk1-7).Positional cloning and genetic studies confirmed that a point mutation in the SPIKE1(SPK1)gene,abt1-1 is a new allele of SPK1.Previous studies have established that SPK1 regulates multiple developmental processes through the SCAR/WAVE-ARP2/3 complexes and the actin cytoskeleton.Although null spk1 mutants are lethal and show defects in plant stature,trichome and epidermal pavement cell development,only trichome branching is affected in spk1-7.Surprisingly,we found that SPK1 is involved in the positioning of nuclei in the trichome cells.Lastly,double mutant analysis revealed synergistic genetic interactions between spk1-7 and mutants of trichome branching regulators,AN and ZWI,and established a functional link between SPK1 and microtubule cytoskeleton.In summary,this study presented a fully viable new mutant allele of SPK1 and shed new light on the regulation of trichome branching and other developmental processes by SPK1.(1)Comparing the epidermal cells and plant phenotypes of the SPK1 allelic mutants,spk1-7,spk1-5,spk1-6,proved SPK1 can regulate the development of plant stature,leaf and epidermal cell morphology.However,mutation of spk1-7 only effects the differentiation development process of trichome.(2)Through detecting the accumulation of transcripts of cell cycle related genes by quantitative PCR and counting nucleus DNA content in WT,spk1-7,and spk1-5,we found that reduction of trichome branches in spk1-7 is not associated with the cell cycle and cell nucleus DNA content changes.(3)Through the observation of nulei trichome positions in the wild type,spk1-7,and spk1-5 plants,we found that most of the trichome nuclei are located at the its branches in spk1-7,spk1-5 plants,while at the stalk in the wild type plants.these data indicated that SPK1 plays a significant role in nuclei positioning.(4)By genetic crossing and the observation of the trichome branching phenotypes,we found the most of the trichomes of the spk1-7 an,spk1-5 an,spk1-6 an double mutant,and the spk1-7 zwi,spk1-5 zwi,spk1-6 zwi double mutants are one branched,demonstrating the genetic interactions between SPK1,AN and ZWI.(5)We found the arrangements of the microtubule arrays in the pavement cells of the spk1-5 and spk1-6 mutants resette leaves is insignificantly different from that in the wild type plants.In the microtubule arrangement relatively order of demonstrating that different mutations of the SPK1 directly affect the microtube array.(6)By detecting the nuclei localization in the spk1-7,an,zwi,spk1-7 an,spk1-7 zwi,an zwi,spk1-7 an zwi mutants,we found that SPK1 might contribute to the regulation of the migration of the trichome nuclei,while AN and ZWI tend to serve for the c MTs arrays dynamic during trichome branching,and they work together to define the precise trichome branching events.