Expression Pattern Analysis Of Stress Associated Protein(SAP) Genesand Function Analysis Of IbSAP15 And IbSAP16 In Sweetpotato,Ipomoea Batatas(L.) Lam.

Abiotic stressesare adverse environmental conditions affecting plant growth and development.At present,the main methods to improve the stress tolerance of plants include the breeding of adverse-resistant crops,stress-tolerance exercisingin plants,and molecular-genetic manipulation.Stress-Associated Protein(SAP)gene family,encoding A20/AN1 zinc-finger domain containing proteins,response to a variety of abiotic stresses and enhance the stress tolerance of plants.Therefore,SAPs are regarded as candidate genes for improving abiotic stress tolerance in crops.In this research,we searched the thanscriptome for sweetpotato unigenes representing IbSAP gene family members,verified their CDS seqences,performed the bioinformatics analysis and transcription analysis;we also primarily analyzed the function of two of the IbSAPs.The main results and conclusions were summarized as follows:1.By searching the sweetpotato transcriptome sequences,24 SAP genes were identified in sweetpotato,and 18 of them contain full-length CDS.We confirmed th sequences and structures of these 18 genes by PCR amplification in both genomic level and transcriptome level.Although their full CDS lengths rangefrom 429 bp to 885 bp,all these 18 IbSAP genes encode A20/AN1 zinc-finger domain containing proteins.All the 18 IbSAPshave homologous genes,ItrSAPs,in its wild relative,Ipomoea trifida.We did alignment of IbSAPs and SAPs in other plants,and built an un-rooted phylogenetic tree with 14 Arabidopsis,13 tomato,18 rice,11 maize as well as 18 sweetpotato SAP protein sequences.The results proved that IbSAPs belong to the SAP genes family.2.By q RT-PCR analysis,the expression pattern of IbSAPs in different tissues or under stresses was made clear.Most of the genes show the highest mRNA level in leaf,tuberous root,pencil root or fibrous rootand the lowest or next to the lowest mRNA level in stem.This difference in expression pattern between IbSAP genes in different tissues may indicate their diversefunctions in sweetpotato.All the 18 full-length IbSAPs were induced by salt or drought stresses,as well as ABA treatment.And most of the IbSAP genes were rapidly induced by bothabiotic stresses.3.IbSAP15 and IbSAP16 encode proteins containing2 AN1 domains but no A20 domain.We overexpressedIbSAP15/IbSAP16 in wild type Arabidopsis thaliana(Col-0).The germination rate and root growth status of both transgenicArabidopsis thaliana undersalt or drought stresses were significantly or extremely significantly improved in comparisonto wild type.These results indicate that IbSAP15 and IbSAP16 are stress tolerantgenes.