Cauliflower is Terrifying

Take a deep breath because the following is disturbing.

Cauliflower has a tumor where its reproductive organs are supposed to be.

That’s right, cauliflower ‘curd’ is a mass of undifferentiated, over-proliferating, non-functional tissue filling each spot that would otherwise contain a normal flower.

Who could have created such a monster?  Those guys from Jurassic Park?

Surprisingly, cauliflower’s curséd curds were bred from Brassica oleracea, a tiny, unassuming wild cabbage that has also produced many non-terrifying crop plants.

Over the past 2000 years, Mediterranean and European farmers have been genetically manipulating Brassica oleracea by selecting the most delicious and nutritious plants in their fields.

Here are a few Brassica oleracea subspecies that you’ll recognize.  These are all the same species of plant, even though they look and taste quite different:

Kale has expanded leaves.

Brussels sprouts have expanded lateral buds.

Kohlrabi has an expanded stem.

Cabbage has an expanded terminal bud.

Broccoli has an expanded floral area.

AND THIS TUMOROUS MASS HAS TERRIFYING WHITE LUMPS!!

I mean, cauliflower has a curd.  Ahem.

As you can see, the edible part of most Brassica oleracea cultivars is a clearly identifiable plant organ that was expanded through breeding.  But not so with cauliflower.  Where does cauliflower get its shapeless blobs?

Back in the ’90s, researchers uncovered the cause of cauliflower’s messed-up masses: a mutation in a transcription factor affecting flower development.  Transcription factors control whether other genes’ DNA is used to make RNA, so they can affect many processes at once.

The researchers were working on Arabidopsis thaliana, a plant that is in the same family as Brassica oleraceae but is easier to grow in the lab.  They found a mutant Arabidopsis plant with flowers that looked exactly like tiny cauliflower heads.  It turned out that the plant that had mutations in both APETALA1, a known transcription factor affecting flower development, and in a second, very similar transcription factor.   Researchers named the second gene CAULIFLOWER.*

Plants that only lack the functional CAULIFLOWER gene but not the APETALA1 gene look normal.  It’s only when both are mutated in the same plant that Arabidopsis flowers look like tiny cauliflowers.

Scientists then confirmed that CAULIFLOWER (the gene) was mutated in cauliflower (the Brassica vegetable).  The APETALA1 equivalent was mutated as well.  They’d found the right genes!

Interestingly, both CAULIFLOWER-only mutants and APETALA1-only mutants in Brassica oleraceae have small curds.  Farmers probably selected for one mutation first and the second mutation later.  Thus, unknowing farmer-geneticists forever changed the crudités platters of humanity.

Who knows how the intrepid ’90s plant scientists kept their sanity as they peered into the dark abyss of cauliflower’s fear-inducing folds?  Those who escaped brought back the key to the madness: two of the crucial transcription factors that tell plant tissue to turn into flowers are missing.

Without the CAULIFLOWER gene, plant floral tissue cannot take on its identity.  Lost in the void, stuck in limbo, cauliflower becomes the most terrifying thing of all: nothing.

So the next time your friend offers to roast cauliflower for dinner, you should run away screaming with your hands over your head shouting about the obscene power of selective breeding.  It’s what any sane person would do.

 

Footnotes:

*In plant biology, genes are often named after their loss-of-function phenotype; in other words, what a plant looks like when it doesn’t have a functional copy of the gene.

For example, Arabidopsis seedlings with a nonfunctional TOPLESS gene make no top, just more roots. Derpy!

Check out fellow plant blogger Arif Ashraf’s ‘mutant series’ to see mutants named after werewolves and bald guys.

**If you were wondering, cauliflower will eventually produce flowers and seeds if you leave it growing for a second year.  That’s how this horror continues to spread.

 

Sources & Further Reading:

‘No Smoking OMG’ gif by Feliks Tomasz Konczakowski

Ashraf, Arif.  “Why Arabidopsis Why: Cauliflower.” ARIBIDOPSIS, 2016. http://www.aribidopsis.com/2016/01/why-arabidopsis-why-cauliflower.html

“Brassica oleraceae (Botrytis Group).”  Plant Finder.  Missouri Botanical Garden, 2017.  http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=261913

Kempin, S.A., Savidge, B., Yanofsky, M.F.  1995.  Molecular basis of the cauliflower phenotype in Arabidopsis.  Science 267.5197: 522.

Long, J.A., Woody, S., Poethig, S., Meyerowitz, E.M., Barton, M.K.  2002.  Transformation of shoots into roots in Arabidopsis embryos mutant at the TOPLESS locus.  Development 129.12: 2797-2806.

Lowman, A.C., Purugganan, M.D.  1999.  Duplication of the Brassica oleraceae APETALA1 floral homeotic gene and the evolution of domesticated cauliflower.  Journal of Heredity 90.5: 514-520.

Osnas, Jeanne.  “The extraordinary diversity of Brassica oleracea”.  The Botanist in the Kitchen, 2012.  https://botanistinthekitchen.blog/2012/11/05/the-extraordinary-diversity-of-brassica-oleracea/

Smith, L.B. and King, G.J.  2000.  The distribution of BoCAL-a alleles in Brassica oleracea is consistent with a genetic model for curd development and domestication of the cauliflower.  Molecular Breeding 6: 603-613.

Smyth, D.R.  1995.  Flower Development: Origin of the cauliflower.  Current Biology 5.4: 361-363.

Szemenyei, H., Hannon, M., Long, J.A.  2008.  TOPLESS Mediates Auxin-Dependent Transcriptional Repression during Arabidopsis Embryogenesis.  Science 319.5868: 1384-1386.