[香蕉基因组]Banana Genome

2012/07/30 22:06:48

The banana (Musa acuminata) genome and the evolution of monocotyledonous plants

Angélique D’Hont, France Denoeud, Jean-Marc Aury, Franc-Christophe Baurens, Françoise Carreel, et.al

Nature (2012) doi:10.1038/nature11241 

Bananas (Musa spp.), including dessert and cooking types, are giant perennial monocotyledonous herbs of the order Zingiberales, a sister group to the well-studied Poales, which include cereals. Bananas are vital for food security in many tropical and subtropical countries and the most popular fruit in industrialized countries. The Musa_domestication process started some 7,000 years ago in Southeast Asia. It involved hybridizations between diverse species and subspecies, fostered by human migrations, and selection of diploid and triploid seedless, parthenocarpic hybrids thereafter widely dispersed by vegetative propagation. Half of the current production relies on somaclones derived from a single triploid genotype (Cavendish). Pests and diseases have gradually become adapted, representing an imminent danger for global banana production. Here we describe the draft sequence of the 523-megabase genome of a _Musa acuminata doubled-haploid genotype, providing a crucial stepping-stone for genetic improvement of banana. We detected three rounds of whole-genome duplications in the Musa lineage, independently of those previously described in the Poales lineage and the one we detected in the Arecales lineage. This first monocotyledon high-continuity whole-genome sequence reported outside Poales represents an essential bridge for comparative genome analysis in plants. As such, it clarifies commelinid-monocotyledon phylogenetic relationships, reveals Poaceae-specific features and has led to the discovery of conserved non-coding sequences predating monocotyledon–eudicotyledon divergence.

Figure 1: **Chromosomal distribution of the main M. acuminata genome features. **Distribution of genes and transposable elements (left) and paralogous relationships between the 11 chromosomes indicated with 12 distinct colours corresponding to the 12 Musa a/b ancestral blocks (right). LINEs, long interspersed elements.

Figure 2: Whole-genome duplication events. a, Paralogous relationships between chromosome segments from Musa α/β ancestral blocks 2 (red) and 8 (green). The 12 Musa α/β ancestral blocks are shown in different colours on the circle. b, Orthologous relationships of Musa ancestral blocks 2 and 8 with rice ancestral blocks ρ2, ρ5 and σ6. We did not observe a one-to-one relationship between, for instance, Musa α/β ancestral block 2 and one ρ ancestral block, which suggests that the γ and σ duplications are two separate events. c, Representation of the deduced WGD event.

Figure 3: Timing of whole-genome duplications relative to speciation events within representative monocotyledons and eudicotyledons. Boxes indicate WGD events. Green boxes indicate WGD events analysed in this paper. All nodes have 100% bootstrap support in a maximum likelihood analysis. Branch lengths (synonymous substitution rate) are indicated. The timing of the β WGD event relative to the Musaceae/Zingiberaceae split remains to be clarified.

Figure 4: Six-way Venn diagram showing the distribution of shared gene families (sequence clusters) among M. acuminata, P. dactylifera, Arabidopsis thaliana, Oryza sativa, Sorghum bicolor_and _Brachypodium distachyon genomes. Numbers of clusters are provided in the intersections. The total number of sequences for each species is provided under the species name (total number of sequences/total number of clustered sequences).

Nature：香蕉基因组测序完成

关于香蕉正濒临灭绝境地的报道很有可能被严重夸大了。至少这是一个科学家小组所希望的。这个小组的科学家终于完成了香蕉基因组的测序，并指望借此来获得新的抗性基因，以使香蕉免遭它的两个真菌“敌人”——黄叶病和黑斑病的侵袭。

世界上超过一半的香蕉和几乎所有出口到美国和欧洲的香蕉，都属于一种名为“卡文迪许”的香蕉。

“卡文迪许”香蕉没有种子，不能进行有性繁殖。这意味着所有香蕉的基因都是相同的，而且都同样容易受到真菌的威胁。

同时，“卡文迪许”香蕉拥有三条染色体，这使得它的基因组测序非常困难。

因此，在一项于7月12日在线发表在《自然》（Nature）志上的最新研究中，研究人员对另一个被称为DH Pahang的香蕉品种的基因组进行了测序。

DH Pahang香蕉是形成“卡文迪许”品种的三种香蕉之一，而且它对威胁“卡文迪许”香蕉的黄叶病具有很强的抵抗力。

更重要的是，正如右图中DH Pahang香蕉的种子所示，它有着完整的“性生活”。这意味着，DH Pahang香蕉可以被用来培育新的品种，或许其生命力要比今天的香蕉更为顽强。