| Plants have as many as over a thousand small signaling peptides(SSPs),also known as plant peptide hormones,which play important roles in regulating various processes in plant growth,development and defense response.Only a very small portion of SSPs have been preliminarily studied and the knowledge about the related genes and action mechanism was very limited.Thus to identify SSPs,to explore the relevant functional genes,to reveal the underlying mechanism,to explore the application potential in crop production are of great theoretical and practical significance.In this thesis,several SSPs or the synthesized short peptides of conservative sequence of some SSPs have been employed,the regulation of small signaling peptide in Arabidopsis root growth,development and mineral uptake have been preliminarily studied,and the main results are as follows:1.Based on the previous research in this laboratory,it has been verified that the synthesized short peptide BIN7 containing only 7 amino acid residues(YIYEVAK)has the function of regulating the Arabidopsis root growth and development.It was found that the effects of BIN7 to the root system of Arabidopsis were similar to that of a phytohormone,i.e.promotion at low concentration versus inhibition at high concentration.To identify the SSPs relevant functional genes,EMS mutagenized Arabidopsis thaliana population was used as the material.MS mediums at a series of BIN7 concentrations were used to screen the mutants insensitive to BIN7,and several insensitive strains were initially obtained after analyzing their BIN7 responses.The response patterns to BIN7 of the selected BIN7 insensitive mutants were verified.These mutants laid the foundation for further cloning of functional genes.2.Artificially synthesized a short peptide according to the conserved amino acid sequence(RPPFKLIPN)of a plant SSP,the Casparian strip integrity factors(CIFs).Synthetic RPPFKLIPN short peptide(CIF)at low concentration was used to treat Arabidopsis seedlings and their roots,the effects of the CIF peptide on the formation of Casparian strip in Arabidopsis roots have been observed by jointly using the confocal microscope and propidium iodide(PI)staining.It was found that CIF treated roots has stronger stained cell walls with wider fluorescence bands in the endodermis cells related to cell wall thickening.To explore the effects of CIF on the uptake and accumulation of mineral elements were studied using the plasma emission spectrum mass(ICP-MS)method.The results showed that CIF significantly affected the uptake and accumulation of most analyzed minerals.For most of the RT-q PCR analyzed mineral transporter genes,treatment by CIF also changed their gene expression.This experiment also showed that CIF has similar function to the 21-amino acid mature CIFs peptide.3.The effects of BIN7 and CIF on the growth and development of rice and rapeseed were analyzed.It was found that seed soaking using 10 ?M BIN7 could promote seed germination both in rice and rapeseed,while seed soaking using 0.1 ?M CIF showed no obvious effects.Adding BIN7 to the growth medium showed that low concentration(10 ?M)BIN7 promoted the seedling growth(root,stem and leaf)both in rice and rapeseed,while high concentration(300 ?M)BIN7 inhibited the growth.Adding low concentration(0.1 ?M)CIF to the nutrient solution in hydroponics system for rice seedlings showed no effects on the growth of new roots.To summarize,the research results regarding two SSPs of BIN7 and CIF accomplished in this thesis could offer valuable references in the identification of functional genes,elucidation of regulating roles in root growth,development and mineral uptake,as well as the exploration for new regulation measures and plant growth regulator products based on SSPs in crop production practice. |
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