Flower power lies in genome down­siz­ing

DNA dump­ing may be the an­swer to Charles Dar­win’s “abom­inable mys­tery”.

Cosmos - - Digest -

Un­til about 140 mil­lion years ago, the world was dom­i­nated by conifers and ferns. Then flow­er­ing plants ex­ploded onto the scene, con­quer­ing the planet with a speed that Charles Dar­win, who liked his evo­lu­tion slow, called “an abom­inable mys­tery”.

Botanists have long cred­ited this suc­cess to the flow­ers’ abil­ity to se­duce dif­fer­ent an­i­mal species into spread­ing their pollen.

A dif­fer­ent and sur­pris­ing ex­pla­na­tion now comes from Kevin Si­monin at San Fran­cisco State Univer­sity and Adam Roddy at Yale Univer­sity. Suc­cess, they ar­gue in the jour­nal PLOS, re­sulted from genome down­siz­ing.

Smaller genomes meant flow­er­ing plants could make smaller nu­clei (which pack­age up the genome in­side the cell) and ul­ti­mately make more com­pact cells, says Si­monin. More com­pact cells, “like smaller Lego blocks”, al­lowed them to pack their leaves more densely with struc­tures like breath­ing pores (stom­ata) and densely branched veins.

That ex­plains why flow­er­ing plants can pho­to­syn­the­sise at three times the rate of ferns and grow much faster.

“They couldn’t do that with­out the in­fra­struc­ture,” says Tim Bro­dribb, at the Univer­sity of Tas­ma­nia. “This is what al­lowed them to over­run the planet.”

In their study, “Genome down­siz­ing, phys­i­o­log­i­cal nov­elty, and the global dom­i­nance of flow­er­ing plants”, Si­monov and Roddy won­dered if the size of plant genomes was linked to the size of cells.

To find out, they stud­ied 400 species of ferns, gym­nosperms (“naked seed” pro­duc­ers such as conifers) and flow­er­ing plants. The smaller the genome, they found, the tinier the cells and the greater the den­sity of leaf stom­ata and veins.

The great­est vari­a­tion was within flow­er­ing plants. A rare Ja­panese flower, Paris japon­ica, boasts the planet’s big­gest genome at 150 bil­lion base pairs of DNA. The small­est genome for a flow­er­ing plant is the car­niv­o­rous Gen­lisea au­rea, with 63 mil­lion base pairs.

CREDIT: MARJETA SUSTARSIC / GETTY IM­AGES

By shrink­ing their genome, flow­er­ing plants were able to shrink their cells and pack in more fea­tures.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.