Study Of MicroRNAs Respond To Low-phosphorus Stress In Maize

Phosphorus is an essential element to plant growth and development process,and known as one of the three most important elements that include nitrogen and potassium.However,it is a common phenomenon that lacking of available phosphorus in soil worldwide.Facing to phosphorus deficiency,plants develop some adaptation mechanisms in morphology,physiology,biochemical and molecular level and so forth.As the the most important crop un the world,maize have great demands for phosphorus.And it was serious to harvest if there is a long-term deficiency of phosphorus.Maize seedlings will take a series of measures to cope with low phosphorus stress,such as root length increased,increasing the number of lateral root and so on.However,the mechanism that response to phosphorus deficiency in maize is unclean.As an important factor of regulation,microRNA play a key role in process of responding to low phosphorus stress in the Arabidopsis,Soybean and some other plants.Therefore,the study of microRNA related with low phosphorus stress in corn becomes necessary.Currently,the number of known microRNA in corn is quite smaller than other species,and miRNA related with low phosphorus stress have not been reported.In this study,eight libraries of maize low phosphorus tolerant inbred line X178 that treated by different phosphorous levels and times have been constructed.Using solexa high-throughput sequencing method,eight libraries have been sequenced.Basic information of data and expression difference of known miRNA have been analyzed.Also,miRNA target genes and novel miRNA have been predicted.Results are as follows:(1)By using high-throughput sequencing technology,there are 44471443 high quality tags(16-30nt)from 87951721 raw tags.The length of these tags distribute primarily from 21-24nt,especially at the 24nt.(2)Comparing with maize genome databases,Rfam databases and Repbase databases,there are 5668244 perfect matched small RNA classified.(3).Using perfect matched small RNA to compare with miRBae database,there are 881 known miRNA from 32 miRNA family and 443 specific target genes.miRNA distribute among all of the 10 chromosomes.The length distribution of miRNA are among 21-24nt,especially at 21 nt.(4)107 known microRNAs belong to 22 miRNA families such as miR156,miR166,miR 169 and so on are identified through analyzing of differential expression.Via analyzing differential expression miRNAs,there are 32 types of miRNA expressing in leaf only,and 35 types of miRNA in root only.Additionally,38 types of miRNA express after treated 12 hours only,and 20 numbers after treated 24 hours only.Also,15 miRNAs have consensus expression are identified in leaf at two different times.Still,11 miRNAs have consensus expression are identified in leaf at two different times.There are 15 miRNAs have consensus expression both in leaf and root after treated 12 hours.And the number of this is 10 after treated 24 hours.(5)301 of total 881 miRNAs used to predicet 443 target genes.Target genes are classified by their functions.(6)22 miRNA families related to low phosphorus are classified to six classification:transcription factors,enzymes,stress sespones,signal transduction,low phosphorus stress responses,unknown.(7)583 novel miRNAs matched with 543 pre-miRNAs are predicted.And 4 novel miRNAs are related to low phosphorus tress.