Cloning And Functional Analysis Of Potassium(K~+) Transporters In Potato

Potassium is a major nutrient in plants,which plays an important role in plant metabolism,growth and stress adaptation.Potassium-deficient plants have a very common phenotype,which is characterized by hindered growth and slow accumulation of nutrients,resulting in a decrease in crop yield and quality.The growth and development of potato needs a large amount of potassium,which is very important for its metabolic function,which can promote the transfer of sugar produced by leaf photosynthesis to the underground part and convert sugar into starch in tuber.This is important for controlling the osmotic potential of cells and maintaining water balance.Due to the high demand for potassium,plants need to effectively absorb potassium from the soil from the roots and further transport it to the plant,and then transport it to different cells at an appropriate concentration.When potassium is absorbed or released into the xylem cavity from the soil solution,these processes need to pass through the plasma membrane and through the tonoplast in the process of transport to the vacuole.The transmembrane transport of potassium can be through potassium channels,using the membrane potential difference to transport along its electrochemical gradient or through potassium ion transporters.Since potassium ion transporter was identified from barley(Hordeum vulgare)and Arabidopsis thaliana,the study of this ion transporter has been more and more in-depth.It is now clear that the main function of these transporters is to regulate the transport of potassium and other alkaline cations in different plant organs and tissues.However,the identification and analysis of potato(Solanum tuberosum)potassium transporter family has not been reported.In this study,the family was identified and classified by bioinformatics methods,and its phylogenetic relationship,gene duplicated events,promoter regulatory elements,gene functional annotation were analyzed,and its gene expression pattern under potassium deficiency was studied by q RT-PCR technology.Further functional studies were carried out on the two screened genes StHAK12 and StKCO2.The main conclusions are as follows:1.A total of 33 K~+transporter genes were identified by genome-wide analysis.Based on the conserved domain analysis,they were divided into five subfamilies:KUP/HAK/KT transporter family,KCO family,Shaker K~+channel family,K~+/H~+antitransporter family and Trk/HKT family.The study of gene duplicated events shows that the evolutionary direction of the above genes is under purified selection,and the function of the family tends to be conservative in the process of evolution.Promoter regulatory elements play a key role in potato response to biotic and abiotic stresses.Potato K~+transporter genes contain three types of cis elements,which are plant hormone responsive elements,abiotic stress responsive elements and light sensitive elements.2.Gene expression pattern is the key to the study of gene function.Based on the results of RNA-seq,the expression patterns of potato K~+transporter genes under different tissues,hormone treatments and abiotic stress were analyzed.Most of the genes were expressed in at least one tissue of potato.Some genes show specific or dominant expression in potato tissues,such as StHAK7 and StK4 are specifically expressed in potato roots,which may be mainly involved in K~+transport or other biological processes in potato roots.Some genes,such as StHKT1 and StKCO5,may play a key role under high temperature and ABA stress,respectively.Genes responding to salt stress and osmotic stress often have the same expression pattern,such as StKCO4 and StK2,which may change the osmotic potential in cells by regulating the transport of potassium ions or other cations in potatoes.so as to enhance the adaptability of plants to hormonal and abiotic stresses.Based on the quantitative expression analysis of K~+transporter in potato under potassium deficiency and control treatments,most of the genes were up-regulated in stems,which may be involved in phloem matter and nutrient transport to regulate nutrient balance in plants to adapt to potassium deficiency stress.3.Overexpression of StHAK12 and StKCO2 in yeast system can significantly enhance the resistance of yeast to heat,salt and osmotic stress.Overexpression of StHAK12 can significantly enhance the resistance of Arabidopsis to salt stress.At the same time,under two different levels of low potassium stress,StHAK12 overexpression line could weaken the adverse effects of potassium deficiency on plants,and was significantly better than the wild type in plant growth and root length,indicating that overexpression of StHAK12 could mediate high affinity transport under low potassium condition,realize the absorption of potassium ions,and improve the tolerance of plants to low potassium stress.Subcellular localization showed that the expression product of StHAK12 was located in the plasma membrane.Based on the above results,it can be concluded that overexpression of StHAK12 can enhance the salt tolerance of plants,and the potassium transporter gene is expressed on the cell membrane,which can maintain the K~+uptake in high Na~+environment and the dynamic balance of K~+/Na~+in cells,thus enhancing the salt tolerance of plants...