Response Of GCP4 To Enhanced UV-B Radiation In Arabidopsis Thaliana

This study investigated the abnormal phenomenon of"Partition-Bundle Division" caused by UV-B stress that affects mitotic plant cells.Previous work on the response of the microtubule cytoskeleton to UV-B indicated that it is accompanied by this phenomenon.The microtubule in plants was shown to not only play an important role in the growth and development of every growth stage,such as mitosis,cytokinesis,organelle transport,and morphogenesis,but in the perception and transmission of stress-induced signals from the environment.The microstructure of microtubules themselves is complex.As the expression of?-tubulin complex 4(GCP4)in microtubule nucleation decreases,a similar abnormal phenomenon appears,which manifests in the formation of non-spindle poles and non-phragmoplast polarity as well as scattered spindle and phragmoplast.Therefore,this study investigated GCP4 in Arabidopsis roots,by studying the function of GCP4 during gametophyte development.Studying GCP4 changes in the root meristem in response to UV-B stress further uncovers the relationship between microtubules during UV-B stress.This study provides a basis for the effects of GCP4 during UV-B radiation and elucidates the mechanism of cell division through the effects of microtubules.The main results can be summarized in the following:(1)This study used MBD-GFP Arabidopsis plants,which were exposed to different UV-B doses.The suitable UV-B radiation doses were identified,depending on the changes of microtubule arrays,especially spindles and phragmoplast.The results showed that 6 h of light repair were required after exposure to UV-B at a dose of 7.2 KJ/m~2.(2)Exposure to 7.2 KJ/m~2 UV-B stress for 6 h,depolymerized microtubules,reduced microtubule arrays and the cell division phase,and changed the misaligned cell walls.(3)Screening of Arabidopsis gcp4 mutants showed that T-DNA insertion of the 54th nucleotide T of the third intron caused a lethal phenotype,and only heterozygous plants were produced.(4)gcp4/gcp4 GCP4-GFP complement Arabidopsis were obtained through the construction of p GCP4::GCP4CDS:GFP.Then,the colocalization of GCP4 was observed in the cytoplasm,the nuclear envelope,and the plasma membrane.(5)Treatment of gcp4/gcp4 GCP4-GFP Arabidopsis after UV-B stress achieved a patchy or blocky-like distribution in meristem cells in root tips,as well as a curved nucleus and decreased transcription level of the GCP4 gene.(6)The relative expression of the GCP family was increased after treatment with 7.2 KJ/m~2 UV-B for 6 h light repair.(7)According to the gametophyte transmission efficiency statistics,GCP4 plays an important role during gametophyte development;however,the effect on the male gametophyte is lower than that on the female gametophyte.(8)The complement Arabidopsis partly recovered the lethal phenotype and defective gametophytic development,suggesting that GCP4 genes play a key role in the formation and development of germ cells.In conclusion,the UV-B stress signal affects microtubule dynamics.The instability of microtubules may be critical in the process of receiving UV-B signals and the quick plant response.Maybe GCP4 plays a role in assisting in response to UV-B signals,which seems likely since it is an essential factor in the growth and development of plant cells.GCP4defects cause defects in gametophyte development,transmitted by the parents to offspring,which then leads to abortive seeds.Thus,the study of abiotic stress through microtubules and their nucleation factors may be a novel approach for the plant defense.