Transposons and Color was Virused Bulbs

Leo A. Martin
Wed, 09 Apr 2014 18:22:56 PDT
To my understanding, many cultivated flowering plants with colored or white flowers on
different plants reveal simple Mendelian inheritance of pigment production. That is, the
wild type plant has colored flowers, reflecting one functioning set of color genes on
each of the pair of chromosomes governing flower color, whereas white-flowered plants
have two sets of defective pigment production systems. Having two of the same gene
complexes is referred to as being homozygous and having one normal and one abnormal is
referred to as being heterozygous. So, plants having two functioning complexes would be
referred to as being wild type homozygous, plants with two abnormal complexes would be
referred to as being aberrantly homozygous, and plants with one of each would be

In some cases plants having one chromosome with functioning pigment genes and one
without functioning pigment genes (heterozygous) have the normal flower color, and in
other cases they have paler flowers (think red, white and pink in sweet peas / Lathyrus

If two wild-type homozygous plants breed, all their progeny will have normal flower
colors (barring new mutations.) If two aberrantly-homozygous plants and white flowers
breed, all their progeny will have white flowers. If one wild-type homozygous plant
breeds with one homozygous-aberrant plant, all the progeny will be heterozygous, with
one normal gene complex and one abnormal gene complex, and all will have colored
flowers, since all will produce some pigment. But if two of these heterozygous plants
breed, a quarter of their progeny will be wild-type homozygous, a quarter will be
aberrantly homozygous, and half will be heterozygous.

How them to explain flower color in Bombax ellipticum? (Or perhaps Pseudobombax
ellipticum.  I haven't read the paper.) This is a tree from Mexico with a large under-
and above-ground storage trunk. For years it was in Bombacaceae, but a lot of
reassortment has been going on, and I think it is now a kind of cotton. Everybody I know
who has been to habitat during bloom season says all the trees have white flowers.
Almost all its American relatives have white flowers. But there is a form, planted
rarely here and there throughout Mexico, always in cultivation, with red flowers. It can
be seen at the four corners of one of the town squares in Tehuantepec, and in at least
one private garden each in Oaxaca city. This red form does not have the thick bulbous
base of the wild type, and it seems to me the red ones are all cutting-grown. The red
form has similar flowers and leaves to the white form. I know there is a red-flowered
tree in Bombacaceae from tropical Asia, but the Mexican plant does not look to me like
photos I have seen of this species.

How to account for a plant with wild-type white flowers and one instance of a red sport?
Transposons revealing function in an otherwise-silenced red pigment production gene
complex? I don't have the red form so I can't perform crosses to see what happens. I
know a number of people in metro Phoenix with blooming wild-type Bombax ellipticum.

Leo Martin
Phoenix Arizona USA

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