A simple change determines male vs female organ development in flowers

Gene duplication is a  major source of genomic novelty for evolution to work on.  When genes duplicate, the extra copy of the gene is often redundant – it might degrade and become a pseudogene or take on a completely new function.  Alternatively, the function of the original gene might become partitioned between the two duplicates in a process known as subfunctionalization.  An excellent example of this has recently been reported in the genes that control male and female organ development in the flower, and it’s (almost) all down to a single amino acid change between the duplicate genes.

Development of male and female reproductive organs in flowers is controlled largely by a group of genes called MADS-box transcription factors. Different versions of these transcription factors (known as A, B or C function genes) are expressed in different parts of the developing flower, acting either alone or together to produce sepals, petals, stamens (male) or carpels (female)*.

Much of what we know about flower development comes from studies on two “model” plants – Arabidopsis (rockcress) and Antirrhinum (snapdragon).  In these species, and in many other flowering plants, the MADs-box C-function gene that controls the production of carpels vs stamens has duplicated. In Arabidopsis, one of the copies (called AG) makes both male and female organs, but the other copy has taken on the completely new function of making seed pods shatter (and is appropriately called SHATTERPROOF).  However, in Antirrhinum both copies still play a role in sex organ development: one copy (called FAR) makes only male parts, while the other copy (PLE) makes mainly female parts but also has a small role in making male parts.

Thus in Antirrhinum, the function of the original gene (making both male and female parts) has almost been split between the two duplicate copies.  In a study published online in PNAS last week, researchers at the University of Leeds, led by Professor Brendan Davies,  found a surprisingly simple difference in the two copies has led to their profoundly different roles.

New Zealand’s favourite plant

Hot on the heels of Forest and Bird’s “Bird of the year” competition comes the NZ Plant Conservation Network‘s 2009 favourite plant poll.  The winner was announced just before Christmas but I must have missed it in the Christmas rush.  While voters in the bird of the year poll managed to display a stunning lack of originality in picking kiwi as their favourite, plant of the year voters were somewhat more creative, voting Pingao as their favourite native plant for 2009. 

Pingao (Desmoschoenus spiralis, or the golden sand sedge) plays an important role in stabilizing sand dunes so its likely to become increasingly important in the face of climate change.  Who’d have thought it has so many fans? The shadowy and mysterious Pingao Pressure Group was obviously busy lobbying for votes while Pohutukawa advocates were looking the other way.   

Here’s a picture:

(Photo by John Sawyer, NZ Plant Conservation Network)

Others in the top ten include the tree nettle (Ongaonga) at number 2, Chatham Island speargrass, some traditional favourites like Southern rata, Chatham Island forget-me-not and Kakabeak, and the plant with the best name of all, the fish-guts plant.

Photo of the month

I’ve decided to start a couple of monthly series, in order to keep this blog on track and create a few themes.  Photo of the month is quite obvious, but the “rules” are that it will be an native species from the NZ forest, in its natural environment*.

For this month, here is a northern rata flower (Metrosideros robusta) to remind you of summer.  Taken on the slopes of Mt Kapakapanui in the western Tararua ranges, just north of Wellington.   Interesting that the flower was quite yellowish instead of red - can any botanists out there shed some light on why this is?

 

*Rules may be subject to change