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Tuesday, 23 August 2011

Where did Cauliflower come from?????

Cabbage
Cabbage has been a part of our diet for a few thousands of years. Cabbages date back to the era of ancient Greeks and Romans. (600 BC) Roman mythology holds that cabbages sprung from the tears of Lycurgus, King of the Edonians. Not only did the Ancient Romans love cabbage, it has been a delicacy all over the world. Hence the proverbs like "A good wife and a wholesome cabbage soup, what more could you want? "Sauerkraut from Germany or the Korean Kim-chee are few of the international cabbage delicacies. But the old cabbage changed over time to give rise to various other vegetables. It was during this later period  of time (15th Century AD) that cauliflower appeared on earth!
Cauliflower

There has been a constant evolution in the domesticated plants because of the added " human selection factor". e.g. plants with bigger grain size or sweeter fruits etc were preferred by the farmers. They harvested crops with such added characters. This artificial selection gave an advantage to the newer varieties. Over time the original wild type varieties were dominated by the "selected ones" and the added characters became a general feature of the population. This led to the birth of new subspecies and species.


Kohlrabi
In the same way, Domestication of the wild cabbage has led to the evolution  of the Cole family. Cabbage, Broccoli, Cauliflower, Brussels sprouts, Kale, Kohlrabi all belong to the same family and have originated from the wild type cabbage. They have originated through the artificial selection. 







Kale
As a general scheme of plant development, a meristem (dividing and growing tissue of plants) is present at the apex of the elongating shoot. This meristem gives rise to small, undifferentiated primordia and in turn produces leaves and flowers on is flanks. The initial primordia give rise to leaves whereas later ones give rise to flowers. As the plant grows the apical meristem is converted into inflorescence meristem and later into floral meristem. This very pattern of development has been modified in various ways  in the Cole vegetables. Various modified forms were then selected and adopted. Thus the domestication of wild type cabbage gave us many more vegetables.


Brussels sprouts
B.oleracea is the original wild type cabbage which has given rise to various subspecies. The subspecies botrytis, (cauliflower) and italica, (Broccoli) show a modification of inflorescence into large dense structures called as curd. It consists of a dense mass of arrested inflorescence.  In case of cauliflower the inflorescence meristem formation itself is perturbed. whereas in broccoli primary floral meristem and buds are formed which do not develop into true flowers.What might have triggered this change?


Broccoli


Studies in Arabidopsis thaliana (Cousin of Cabbage) have shown that floral homeotic genes are important for early identification of inflorescence meristem (developing reproductive primordia) as a floral meristem.  Leafy, Apetala1 (AP1) and cauliflower (cal) are such genes. cal gene codes for a protein : a MADS-box transcription activator. The K domain of the protein is responsible for its dimerisation. Upon dimerisation Cal protein binds to DNA and assists transcription of genes involved in identification of floral meristem.

It was found out that in cauliflower plants the cauliflower gene indeed has a premature stop codon . This results in  a truncated protein. This protein cannot dimerize and fails to function as a transcription activator.  Hence floral meristem is not formed. Instead the inflorescence meristem branches again and again to form the curd like structure typical to cauliflower. Further studies in Arabidopsis have shown that mutation in both CAL and AP1 gene together cause formation of cauliflower curd like structure instead of flowers. in Arabidopsis plant.  Thus it is these mutations that have turned the cabbage into a cauliflower or a broccoli or a kale! It is these simple changes that have led to the evolution of the Cole family of vegetables.
Current Biology 1995, Vol 5 No 4: Arabidopsis flowers fail to develop and a cauliflower curd like structure is form in ap1 and cal mutant

This is the magic of Biology, it can turn a cabbage into a cauliflower by tweaking a few molecules!

References:
1. Origin of the cauliflower,  Current Biology 1995, Vol 5 No 4
2. Lowman and Purugannan, Duplication of APETALA1 floral homeotic gene, Journal of Heredity 1999
3. Variation and Selection at the CAULIFLOWER Floral Homeotic Gene Accompanying the Evolution of Domesticated Brassica oleracea ,Michael D. Purugganan, Abee L. Boyles and Jane I. Suddith, Genetics 155: 855–862 ( June 2000)

5 comments:

  1. where did it com from

    ReplyDelete
    Replies
    1. Two pieces of Cauliflower

      One day two pieces of Cauliflower, who were best friends, were walking together down the street. They stepped off the curb and a speeding car came around the corner and ran one of them over. The uninjured cauliflower called 911 and helped his injured friend as best he was able. The injured cauliflower was taken to emergency at the hospital and rushed into surgery. After a long and agonizing wait, the doctor finally appeared. He told the uninjured cauliflower, "I have good news, and I have bad news. The good news is that your friend is going to pull through." "The bad news is that he's going to be a vegetable for the rest of his life".

      Delete
  2. Naturally evolved fruit ..imo
    But where did this happen?

    ReplyDelete
    Replies
    1. There has been a constant evolution in the domesticated plants because of the added « human selection factor». e.g. plants with bigger grain size or sweeter fruits etc were preferred by the farmers. They harvested crops with such added characters. This artificial selection gave an advantage to the newer varieties.

      This led to the birth of new subspecies and species.

      Delete
  3. It's a mutation of the inflorescence meristem. It's basically the female part of a flower replicating itself into a curd. Probly an Italian farmer saw this mutation in his field and it was good to eat. So he started to cross breed the plants with this particular mutation. Over time I think they produced a more dense head of cauliflower. As you see an experiment from 1995 picture above. It shows the mutation in the experiment. In the experiment think they basically manipulated CAL and AP1 gene.

    ReplyDelete