甘薯PEBP基因家族鉴定以及影响甘薯块根发育候选PEBP基因的鉴定

Identification of PEBP Gene Family in Sweet Potato and Screening of Key PEBP Genes Regulating Storage Root Development

磷脂酰乙醇胺结合蛋白(PEBP)在植物中广泛存在,在调控开花、种子休眠以及地下储藏器官(如马铃薯块茎和洋葱鳞茎)形成中发挥着重要作用。但目前有关甘薯(Ipomoea batatas)PEBP基因家族成员的研究较少,且尚未有研究系统揭示调控甘薯块根发育的关键PEBP家族成员。本研究首先通过生物信息学分析对甘薯基因组中PEBP基因家族成员的数量和种类进行鉴定,然后通过PEBP基因表达的组织特异性分析、PEBP基因在不同发育时期块根中表达水平的动态变化及其与糖转运蛋白SWEET基因表达水平之间的相关性分析,系统筛选出调控甘薯块根发育的候选PEBP基因家族成员并初步揭示其可能的调控机制。结果如下:(1)从甘薯基因组中共鉴定出15个PEBP基因,聚类分析将其分为4个亚家族:5个FT-like成员(IbFT1~5)、6个TFL1-like成员(IbTFL1~6)、2个MFT-like成员(IbMFT1~2)和2个PEBP-like成员(IbPEBP1~2)。(2)聚类分析结果表明,IbFT5可能会促进甘薯块根发育,而IbTFL3可能会抑制其块根发育。(3)甘薯PEBP基因表达的组织特异性分析表明,在根系高表达的PEBP基因中,只有IbFT5、IbTFL4和IbTFL6不仅在根系的表达水平高于在其他组织中的表达水平,而且和根系中其他PEBP家族成员的表达水平相比,这3个基因的表达水平也是最高的,因此推测这3个PEBP基因可能会促进块根膨大。(4)对上述2种方法得到的4个候选PEBP基因(IbFT5、IbTFL3、IbTFL4和IbTFL6)在不同发育时期块根(定植后30、60、90、120 d)中的表达水平测定结果表明,随着块根的发育,IbFT5、IbTFL4、IbTFL6的表达水平显著上升,特别是在块根快速膨大期(60~90 d),而IbTFL3的表达水平在块根快速膨大期(60~90 d)则快速下降。因此,IbFT5、IbTFL4、IbTFL6可能促进块根发育,而IbTFL3则可能抑制块根发育。(5)伴随着IbFT5、IbTFL4、IbTFL6的表达水平的升高,块根中高表达的5个SWEET基因中有4个(IbSWEET4、IbSWEET11、IbSWEET16和IbSWEET19)的表达水平均呈现不断下降的趋势,这与马铃薯的研究结果相似,表明甘薯PEBP基因可能也是通过抑制SWEET蛋白活性,从而促进糖分通过更高效率的共质体转运途径向块根进行运输最终促进块根发育。综上,本研究不仅确定了甘薯基因组中PEBP基因家族成员的数量和种类,而且还筛选出4个可能影响甘薯块根发育的候选PEBP基因,为进一步提高我国甘薯的产量提供理论依据。

Phosphatidyl ethanolamine-binding protein(PEBP)widely exist in plants and play important roles in regulating flowering,seed dormancy and the formation of underground storage organs(e.g.potato tubers and onion bulbs).However,up to now,there is few studies conducted on PEBP genes in sweet potato(Ipomoea batatas),and there is also no research published to reveal the key members of PEBP gene family that regulate the development of storage root of sweet potato.Our study first identified the number and types of the PEBP gene family in sweet potato through bioinformatics analysis.Then,to screen the candidate members of the PEBP gene family that regulate the development of storage root of sweet potato,the tissue specificity of PEBP gene expression and the dynamic changes of PEBP gene expression level in storage roots at different development stages were analyzed.To explore possible regulatory mechanism,the correlation between PEBP gene expression level and SWEET gene expression level in storage roots were also examined.The results are as follows:(1)A total of 15 putative PEBP genes were identified from the sweet potato genome,which were classified into 4 subfamilies:5 of FT-like genes(IbFT1-5),6 of TFL1-like genes(IbTFL1-6),2 of MFT-like genes(IbMFT1-2),and 2 of PEBP-like genes(IbPEBP1-2).(2)Clustering analysis revealed that IbFT5 may promote the development of storage root of sweet potato,while IbTFL3 may inhibit the development.(3)The tissue specificity analysis of sweet potato PEBP gene expression showed that IbFT5,IbTFL4 and IbTFL6 not only showed higher expression levels in the diverse root tissues than in other tissues,but also had higher expression levels in roots than other PEBP genes.Therefore,it is speculated that the three PEBP genes may promote root enlargement.(4)The expression levels of the four candidate PEBP genes(IbFT5,IbTFL3,IbTFL4 and IbTFL6)obtained from the above two methods were determined in storage roots at different developmental stages(30,60,90 and 120 days after planting).It was found that the expression levels of IbFT5,IbTFL4 and IbTFL6 significantly increased with the development of root tubers,especially during the rapid expansion period(60-90 days),while the expression level of IbTFL3 rapidly decreased during the rapid expansion period(60-90 days).Therefore,all the above measurement results indicate that IbFT5,IbTFL4 and IbTFL6 may promote root development,while IbTFL3 may inhibit root development.(5)With the increase of expression levels of IbFT5,IbTFL4 and IbTFL6,the expression levels of four out of the five highly expressed SWEET genes(IbSWEET4,IbSWEET11,IbSWEET16 and IbSWEET19)in storage roots showed a continuous decreasing trend.This result is similar to the findings in potatoes,indicating that the PEBP gene of sweet potato may also inhibit SWEET activity and thus promotes the transportation of sugar to the storage roots through more efficient symplasmic pathway,which ultimately promotes the development of storage roots.In conclusion,this study not only determined the number and types of members of the PEBP gene family in the sweet potato genome,but also systematically identified four candidate PEBP genes affecting the development of sweet potato storage roots,which can provide a theoretical basis for further improvement of sweet potato yield in China.