Teleost fish with specific genome duplication as unique models of vertebrate evolution

Whole-genome duplication (WGD) is believed to be one of the major evolutionary events that shaped the genome organization of vertebrates. Here, we review recent research on vertebrate genome evolution, specifically on WGD and its consequences for gene and genome evolution in teleost fishes. Recent genome analyses confirmed that all vertebrates experienced two rounds of WGD early in their evolution, and that teleosts experienced a subsequent additional third-round (3R)-WGD. The 3R-WGD was estimated to have occurred 320–400 million years ago in a teleost ancestor, but after its divergence from a common ancestor with living non-teleost actinopterygians (Bichir, Sturgeon, Bowfin, and Gar) based on the analyses of teleost-specific duplicate genes. This 3R-WGD was confirmed by synteny analysis and ancestral karyotype inference using the genome sequences of Tetraodon and medaka. Most of the tetrapods, on the other hand, have not experienced an additional WGD; however, they have experienced repeated chromosomal rearrangements throughout the whole genome. Therefore, different types of chromosomal events have characterized the genomes of teleosts and tetrapods, respectively. The 3R-WGD is useful to investigate the consequences of WGD because it is an evolutionarily recent WGD and thus teleost genomes retain many more WGD-derived duplicates and “traces” of their evolution. In addition, the remarkable morphological, physiological, and ecological diversity of teleosts may facilitate understanding of macrophenotypic evolution on the basis of genetic/genomic information. We highlight the teleosts with 3R-WGD as unique models for future studies on ecology and evolution taking advantage of emerging genomics technologies and systems biology environments.     

冬虫夏草MYB家族基因鉴定及其在生长发育中的表达分析

MYB蛋白是一类广泛存在于真核生物中的转录因子,在真菌的生长发育中发挥调控作用。本研究对冬虫夏草菌中的潜在MYB转录因子家族基因进行了全基因组鉴定和生物信息学分析,并研究了MYB家族成员在冬虫夏草生长发育不同阶段和不同部位的表达模式。结果表明,冬虫夏草MYB转录因子家族包含3个1R-MYB和3个2R-MYB;6个MYB转录因子蛋白均包含近50个保守氨基酸序列,形成螺旋-转角-螺旋的结构。通过分析MYB转录因子基因在不同发育阶段（MYB-1-6）和子实体不同部位（MYB-1、3、6）的相对表达量,发现MYB-1在冬虫夏草整个发育阶段表达较为稳定,MYB-3在子实体成熟阶段（MF）表达量最高,远高于其他阶段,且在MF的顶部可育部分MF-3高表达,表明其可能参与冬虫夏草子实体的有性发育;MYB-6在子座发育初期（YF）的中部YF-2表达量最高,为菌丝阶段（HY）的5倍,表明MYB-6可能参与子座柄部的伸长。     

Arabidopsis MYB26/MALE STERILE35 regulates secondary thickening in the endothecium and is essential for anther dehiscence

The Arabidopsis thaliana MYB26/MALE STERILE35 (MS35) gene is critical for the development of secondary thickening in the anther endothecium and subsequent dehiscence. MYB26 is localized to the nucleus and regulates endothecial development and secondary thickening in a cell-specific manner in the anther. MYB26 expression is seen in anthers and also in the style and nectaries, although there is no effect on female fertility in the ms35 mutant. MYB26 expression in anthers occurs early during endothecial development, with maximal expression during pollen mitosis I and bicellular stages, indicating a regulatory role in specifying early endothecial cell development. Overexpression of MYB26 results in ectopic secondary thickening in both Arabidopsis and tobacco (Nicotiana tabacum) plants, predominantly within the epidermal tissues. MYB26 regulates a number of genes linked to secondary thickening, including IRREGULAR XYLEM1 (IRX1), IRX3, IRX8, and IRX12. Changes in expression were also detected in two NAC domain genes, NAC SECONDARY WALL-PROMOTING FACTOR1 (NST1) and NST2, which have been linked to secondary thickening in the anther endothecium. These data indicate that MYB26 regulates NST1 and NST2 expression and in turn controls the process of secondary thickening. Therefore, MYB26 appears to function in a regulatory role involved in determining endothecial cell development within the anther and acts upstream of the lignin biosynthesis pathway.     

不同灌溉条件下杨树人工林蒸腾过程及环境响应

研究不同土壤水分阈值灌溉下毛白杨(Populus tomentosa)生长季蒸腾与环境因子的关系, 对于科学制定毛白杨高效水分管理策略至关重要。该研究以毛白杨人工林为研究对象, 设置不同灌溉处理: 充分灌溉(DF, 当滴头正下方20 cm处的土壤水势达到-18 kPa时灌溉)、控水灌溉(DC, 当滴头正下方20 cm处的土壤水势达到-45 kPa时灌溉)和无灌溉(CK, 空白对照)。采用热扩散技术, 对毛白杨生长季树干液流通量进行连续观测, 并同步监测太阳辐射(SR)、空气温度(T_a)、空气湿度(RH)、土壤体积含水率(SWC)和风速(WS)等环境因子。结果显示: 1)不同灌溉处理下毛白杨树干液流通量日变化趋势相似, 呈现单峰型, 并存在显著的夜间液流活动。灌溉处理不会影响树干液流的启动时间, 但会造成树干液流峰值时间出现差异, 充分灌溉会使液流峰值到达时间提前。灌溉会增大毛白杨蒸腾量, 毛白杨的蒸腾量随着土壤水分灌溉阈值的减小而增大。2)毛白杨树干液流密度与SR和空气水汽压亏缺(VPD)存在明显的时滞现象, 树干液流通量变化提前于VPD, 而滞后于SR。不同灌溉处理对时滞现象无显著影响。3) 3个处理下, 蒸腾与VPD、SR及SWC具有显著正相关关系, 与风速具有显著负相关关系, 且对气象因子的响应程度不同。综上所述, 灌溉能够有效调节人工林水分生理对环境因子的适应过程, 但增加灌溉未必会造成蒸腾相应增加。根据林分蒸腾需水和自然降雨的关系, 生长季前期(该研究为4-7月)进行灌溉有利于毛白杨人工林水分生理活动的进行。     

甘蓝型油菜BnMYB80基因的生物信息学分析

在高等植物花药发育和花粉形成中, MYB转录因子起着非常重要的作用, 其中MYB80是参与绒毡层发育及引起雄性不育的重要转录因子。该研究以拟南芥(Arabidopsis thaliana) AtMYB80为参考序列, 通过BLAST比对分析, 在白菜(Brassica rapa)、甘蓝(B. oleracea)和甘蓝型油菜(B. napus)中分别获得MYB80基因的2、2和6个同源序列, 运用生物信息学方法对其核苷酸序列及编码的氨基酸序列进行组成成分、亚细胞定位、磷酸化位点、疏水性/亲水性、蛋白质二级、三级结构和功能域分析。结果表明, MYB80转录因子亚细胞定位于细胞核, 具有多个不同的磷酸化位点, 肽链表现为亲水性; 二级、三级结构预测显示, MYB80蛋白以α-螺旋和无规则卷曲为主要结构元件; 保守结构域分析表明, 其N端具有2个串联的SANT功能域, 属于R2R3型MYB转录因子。多重序列比对和进化树分析结果表明, 甘蓝型油菜与白菜、甘蓝的序列相似性大于92%, 且MYB80转录因子的功能结构域具有较高的同源性和较强的序列保守性。该研究结果对深入解析甘蓝型油菜MYB80的生物学功能及育性调控的分子机理具有重要意义, 为甘蓝型油菜杂种优势利用提供了依据。