Media Releases

Self-fertilizing plants contribute to their own demise

June 12, 2013

TORONTO, ON – Many plants are self-fer­til­iz­ing, mean­ing they act as both moth­er and father to their own seeds. This strat­e­gy – known as self­ing – guar­an­tees repro­duc­tion but, over time, leads to reduced diver­si­ty and the accu­mu­la­tion of harm­ful muta­tions. A new study pub­lished in the sci­en­tif­ic jour­nal Nature Genet­ics shows that these neg­a­tive con­se­quences are appar­ent across a self­ing plant’s genome, and can arise more rapid­ly than pre­vi­ous­ly thought.

In the study, an inter­na­tion­al con­sor­tium led by Stephen Wright in the Depart­ment of Ecol­o­gy and Evo­lu­tion­ary Biol­o­gy at the Uni­ver­si­ty of Toron­to and Detlef Weigel at the Max Planck Insti­tute for Devel­op­men­tal Biol­o­gy sequenced the genome of the plant species Capsel­la rubel­la, com­mon­ly known as Red Shepherd’s Purse. They found clear evi­dence that harm­ful muta­tions were accu­mu­lat­ing over the species’ rel­a­tive­ly short exis­tence.

“The results under­score the long-term advan­tages of out­cross­ing, which is the prac­tice of mat­ing between indi­vid­u­als, that gives us the wide array of beau­ti­ful flow­ers,” said Wright. “Self­ing is a good short-term strat­e­gy but over long timescales may lead to extinc­tion.”

Red Shepherd’s Purse is a very young species that has been self-fer­til­iz­ing for less than 200,000 years. It is there­fore espe­cial­ly well-suit­ed for study­ing the ear­ly effects of self-fer­til­iza­tion. By con­trast­ing Red Shepherd’s Purse with the out­cross­ing species that gave rise to it, the researchers showed that self-fer­til­iza­tion has already left traces across the genome of Red Shepherd’s Purse.

“Harm­ful muta­tions are always hap­pen­ing,” said Wright. “In crops, they could reduce yield just as harm­ful muta­tions in humans can cause dis­ease. The muta­tions we were look­ing at are changes in the DNA that change the pro­tein sequence and struc­ture.”

The find­ings rep­re­sent a major break­through in the study of self-fer­til­iza­tion.

“It is expect­ed that harm­ful muta­tions should accu­mu­late in self­ing species, but it has been dif­fi­cult to sup­port this claim in the absence of large-scale genom­ic data,” says lead author Tan­ja Slotte, a past mem­ber of Wright’s research team and now a researcher at Upp­sala Uni­ver­si­ty. “The results help to explain why ancient self-fer­til­iz­ing lin­eages are rare, and sup­port the long-stand­ing hypoth­e­sis that the process is an evo­lu­tion­ary dead-end and leads to extinc­tion.”

The researchers said that with many crops known to be self-fer­til­iz­ing, the study high­lights the impor­tance of pre­serv­ing crop genet­ic vari­a­tion to avoid loss­es in yield due to muta­tions accu­mu­lat­ing.

The find­ings are report­ed in the paper “The Capsel­la rubel­la genome and the genom­ic con­se­quences of rapid mat­ing sys­tem evo­lu­tion” in Nature Genet­ics this week. Oth­er lead col­lab­o­ra­tors on the study includ­ed researchers from the Max Planck Insti­tute in Tübi­gen, Ger­many and the US Depart­ment of Ener­gy’s Joint Genome Insti­tute. The research is sup­port­ed by fund­ing from the US Depart­ment of Ener­gy, the Max Planck Insti­tute, Genome Cana­da and Genome Que­bec.

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Note to media: Vis­it for images relat­ed to the research study described here.

For more infor­ma­tion, please con­tact:

Stephen Wright
Depart­ment of Ecol­o­gy and Evo­lu­tion­ary Biol­o­gy
Uni­ver­si­ty of Toron­to

Sean Bet­tam
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to