巨桉(Eucalyptus grandis)是我国南方重要用材树种,但其抗逆性较差,限制了其栽培范围的扩大和栽培效益的提高.NAC类转录因子是植物特有的转录因子家族,广泛参与植物生长、发育、代谢和逆境响应,其中非生物逆境响应相关的NAC被称为SNAC(stress-related NAC).本研究在巨桉全基因组范围鉴定的166个NAC和文献报道的74个SNAC的基础上,通过进化分析,筛选EgrSNAC家族成员,并分析其基因、蛋白序列结构、染色体定位、共线性关系、基因重复情况和启动子的顺式作用元件,以及不同组织中的表达模式,并对巨桉幼苗进行低温、干旱、高盐、脱落酸(abscisic acid,ABA)和茉莉酸甲酯(methyl jasmonate,MeJA)处理,利用qPCR分析EgrSNAC基因在这些逆境处理下的表达.结果表明,巨桉中共有22个EgrSNAC基因,分别属于ATAF、NAP和AtNAC3亚家族.除EgrSNAC20外,这些基因编码的蛋白均包含典型的NAM结构域的5个子域,对应Motif1~Motif5.22个基因分布在9条染色体上,有4个共线性基因对以及由11个EgrSNAC基因组成的2个串联重复基因区段.启动子顺式作用元件分析显示,EgrSNAC启动子上分布有多种逆境响应元件.EgrSNAC中串联重复基因的组织特异性表达模式类似.4℃低温处理不同时间的qPCR分析表明,除EgrSNAC1、EgrSNAC3和EgrSNAC22外,其他19个EgrSNAC表达均受低温诱导;对干旱有响应的有 19 个EgrSNAC,除EgrSNAC2、EgrSNAC5、EgrSNAC14 和EgrSNAC21表达被抑制外,其他均被干旱诱导;高盐处理下,有19个EgrSNAC表达发生变化,且仅EgrSNAC21被高盐抑制.另外响应ABA(100 μmol/L)处理的14个基因均被诱导;而MeJA(100 μmol/L)处理下表达有变化的基因有13个为诱导型,4个为抑制型.本研究结果揭示了不同EgrSNAC基因与低温、干旱、高盐和ABA、MeJA等非生物逆境因子之间的关系,为进一步研究巨桉EgrSNAC基因资源提供了参考.
Eucalyptus grandis has made important contribution to wood-related industries in South China,but they are sensitive to abiotic stresses,limiting the expansion of its cultivation and benefits improvement of plantation.NAC is a plant-specific transcription factor family,which is widely involved in plant growth,development,metabolism and stress response.And,the stress-related NACs were named SNAC.In this study,166 NAC transcription factors identified in E.grandis genome and 74 SNAC in other plant species were used to identify EgrSNACs.And,EgrSNACs structure,coding protein sequence,chromosome localization,collinearity and gene duplication,cis-acting elements on promoters,and the tissue-specific expression patterns were analyzed.In addition,the seedlings of E.grandis were treated with low temperature,drought,high salt,abscisic acid(ABA)and methyl jasmonate(MeJA),and qPCR was used to analyze the expression of EgrSNACs under these treatments.The results showed that there were 22 EgrSNACs in E.grandis,belonging to ATAF,NAP,and AtNAC3 subfamily.Except for EgrSNAC20,the proteins encoded by these genes all contained 5 subdomains of the typical NAM domain,corresponding to Motif1~Motif5.The 22 EgrSNACs were distributed on 9 chromosomes,with 4 collinear gene pairs and 2 tandem repeat gene segments composed of 11 EgrSNACs.Cis-acting element of promoter analysis showed that multiple stress response elements were distributed on the EgrSNAC promoters.The expression pattern of tandem duplicated EgrSNACs were similar in leaf,stem,xylem and phloem.The qPCR analysis of different time treatments at 4℃indicated that the expression of the 19 EgrSNACs were induced by low temperature,in addition to EgrSNAC1,EgrSNAC3,and EgrSNAC22;there were 19 EgrSNACs that responded to the drought,except EgrSNAC2,EgrSNAC5,EgrSNAC14 and EgrSNAC21 were suppressed,others were induced.Under high salt treatment,19 EgrSNACs expression changes,and only EgrSNAC21 was suppressed.In addition,14 EgrSNACs were induced under ABA(100 μmol/L)treatment.13 EgrSNACs were induced and 4 were inhibited under MeJA(100 μmol/L)treatment.The results of this study revealed the relationship between EgrSNACs and their response of low temperature,drought,high salt,ABA,MeJA and other abiotic stress factors,providing a reference for further study of EgrSNACs in E.grandis.