Function Analysis Of The Protein Transfer Enzyme AtSEC61-? In The Regulation Of Arabidopsis Ca Dependent Growth

Calcium ranked fifth in the content of crustal material.The most abundant element the plant absorbs from the soil is calcium.Extra-cellular Ca²⁺maintains toughness of cell wall and plasma membrane in the millimolar range.Ca²⁺in the cytoplasm is in the micro-molar range and it is the most important second messenger in plant cells.Calcium makes plants to sense stimuli from different environments and internals and increase the plant's corresponding physiological response.In this study,we performed a phenotype analysis 2200 Arabidopsis thaliana membrane protein-related mutant seed banks on different Ca²⁺concentration gradients.After three experimental repeats,we finally selected the AtSEC61-?gene deletion mutant atsec61as an experimental material for further study.To study the function of the AtSEC61-?gene in calcium-dependent physiological features,at first,we performed a phenotype analysis of the AtSEC61-?gene deletion mutant atsec61.The mutant showed yellowing of leaf color,curled leaves,and short plant growth compared to wild-type Col-0 in a low calcium conditions.Phenotype analysis of different concentrations of Fe²⁺,Zn²⁺,Mg²⁺,K⁺and NO₃^-,PO₄^3-revealed that there was a significant difference in growth between mutant and Col-0 under high Mg²⁺condition.In the plant transferring experiment,mutant plants grown on 10?M Ca²⁺and 15 mM Mg²⁺medium were severely inhibited.The contents of total Ca and Mg in AtSEC61-?gene deletion mutant and Col-0 were detected by atomic absorption spectroscopy.We found that the accumulation of Ca in the plants under CK and low Mg²⁺conditions was significantly higher than that under low Ca²⁺and high Mg²⁺conditions.However,the accumulation of Mg was opposite.To study the subcellular localization of AtSEC61-?protein,inoculation of tobacco leaf using recombinant Agrobacterium containing AtSEC61-?-GFP plasmid for transient expression.The result showed that the protein encoded by AtSEC61-?was located in Endoplasmic Reticulum network.Using the Arabidopsis transgenic material expressing AtSEC61-?promoter-driven?-glucuronidase.We found that the promoter of AtSEC61-?gene maintained its activity in young leaves,flowers,pods,and roots.So we get the following conclusions:1)The AtSEC61-?gene plays an important role in plant calcium-dependent growth phenotypes.2)AtSEC61-?gene is involved in the accumulation of Ca in plants.3)The protein encoded by the AtSEC61-?gene is located on the Endoplasmic Reticulum network.4)The promoter of AtSEC61-?gene activates the expression of GUS gene in young leaves,flowers,pods and roots.