《细胞》[Cell]13年6月20日出版pdf全文

nero1981

  R# A! ?# J& W, n2 yVolume 153, Issue 7
& c& Y, M3 n' f+ D, vOn the cover: The mealybug Planococcus citri is host to two bacterial 0 n8 \& B' q4 r) E( G  h. E
endosymbionts with extremely tiny genomes. These symbionts, Tremblaya and : u$ o) q/ Z$ ~4 X3 f
Moranella, live exclusively in specialized insect cells. Remarkably, 0 j. }2 j+ B4 c
Moranella lives inside of Tremblaya; their relationship is the " j3 t& D! E7 o- u# X& U
only known bacteria-within-a-bacterium symbiosis. In this issue, Husnik et al.
& w" U3 [+ ^/ T3 D3 l(pp. 1567–1578) show that this layered symbiosis is enabled by genes that have $ g" s6 g  i9 a8 }+ i- P  t9 K
been horizontally transferred to the insect genome from diverse, historical
/ O( r: I4 g0 q; e# _! b5 Ebacterial infections. These transferred genes are overexpressed in the insect 5 Y$ K2 d1 X4 d2 w. y5 @- _
tissue housing Tremblaya and Moranella and seem to complement
# ^3 Q% G& x. [* q+ N/ f# jseveral symbiont activities. Importantly, these results show that, although the
+ G; y: K0 P( i' z* w! z9 P7 rTremblaya genome rivals some organelles in terms of size and coding
' W* [+ m  B: |0 B3 N: jcapacity, it has not arrived at this state by transferring its own genes to the
# |- i. Y' Y  w% v) p# Ghost genome. Photograph by Alex Wild, University of Illinois.
7 ]3 @8 _) \5 G8 H/ m7 b' [

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