Selected Mutants

From Flower Development, E Coen , Cell & Developmental Biology Department - JIC UK

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JIC Antirrhinum majus Mutant Collection

Over the past 40 years a collection of some 300 to 400 Antirrhinum majus stocks have been built up at John Innes. This collection is the result of intensive genetic studies and comprises various wild types as well as a range of mutants, mainly affecting flower pigmentation, shape or form.

Clicking on the pictures near the mutant descriptions will bring up the high resolution jpeg files for printing and personal use. Please note that all the pictures are protected by copyright and written permission is required for publication and commercial uses; please contact Lucy Copsey for details. Requesting stocks.


Wild Type

The wild type Antirrhinum flower consists of 4 whorls. The outer or 1st whorl comprises 5 sepals, whilst the second whorl is the corolla and consists of 5 lobes ( 2 dorsal, 2 lateral and 1 ventral) which are fused for part of their length to form a corolla tube. 4 stamens make up the 3rd whorl ( the 5th stamen is aborted to form a staminode) and in the centre are 2 united carpels with a style terminating in a stigmatic surface. The corolla of JI wild type lines is fully pigmented, magenta in colour, with a strong patch of yellow in the lip area.


Mutants

Pigment e.g. alleles of the nivea and pallida genes

nivea

This gene is expressed at a very early stage in the biosynthetic pathway to anthocyanin production. Flowers of the null mutant are albino. However, mutants of different nivea lines have produced several independent allelic series. These are maintained in the collection and are the result of transposon activity. The unstable nivea-recurrens-98 line carries Tam3 inserted in the promoter region of the gene. This transposon is highly active and has produced a large number of nivea alleles which have been analysed both genetically and molecularly. They include : unstable, stable, semi dominant spatially patterned and dominant mutations. Independent nivea lines and their allelic series, caused by the activity of Tams 1, 2 or 4 have also been studied.


nivea-recurrens-98


pallida-recurrens

A gene that acts at a late stage in the same biosynthetic pathway as that of nivea. The unstable pallida-recurrens is due to the insertion of the transposable element Tam3 into the promotor region of the gene. The flowers are ivory with randomly distributed red sites and sectors where the transposon has excised somatically. Germinal excision has given rise to an allelic series that has been extensively studied.


Floral Homeotic e.g. floricaula, deficiens and plena

floricaula-640

The vegetative growth and switch to that of the inflorescence is normal. However, instead of flowers being formed in the axil of each bract, a secondary shoot is formed. This shoot in turn produces bracts, within the axils of which further bract-bearing shoots are produced. There is also an unstable allele, floricaula-613.


deficiens-621

The flowers of this mutant have the normal outer whorl of 5 sepals, but the second whorl contains 5 individual sepals rather than the corolla of wild type. The 3rd whorl consists of 5 united carpels, the top of which forms a flattened hollow ring of pollen receptive stigmatic tissue. The 4th whorl does not always develop. This mutant is somatically unstable and clonal islands of petal tissue sometimes develop on the second whorl of sepals.


plena-624

The first and second whorls of the flowers are similar to wild type, whereas the third whorl consists of petaloid structures that are united for most of their length with the petals of the second whorl. The fourth whorl consists of two members with variable structures which show sepaloid, carpeloid and petaloid features. Within the fourth whorl there are upto 5 extra whorls of petaloid structures. This particular allele carries nivea-recurrens-98 . There are further alleles of plena in the collection including:- plena-625 and a dominant allele Ovulata-627.


Inflorescence Architecture - centroradialis

centroradialis-663

The inflorescence (flowering spike) of a wild type Antirrhinum is indeterminate and is controlled by the centroradialis gene. A mutation in this gene causes the inflorescence to become determinate: approximately 9 normal wild type flowers grow up the spike, which is then terminated by a flower with altered symmetry.


Flower shape and symmetry e.g. cycloidea , dichotoma and radialis

cycloidea-608

This mutant has a semi-peloric phenotype and two variations of flower form are seen.

Type 1: which comprises 6 petals and 4 to 5 sepals. The 2 dorsal petals are much reduced and are slightly curved, giving the petals a more lateral shape. The lateral petals have become ventralised and the ventral petal is the same as seen in wild type.

Type 2: This form has 1 central dorsal petal that is much reduced and curved, 2 lateral petals and 3 ventral petals, giving 4 lips instead of the 2 of wild type. The corolla tube in both types is slightly flattened with 5 nectary regions. Sometimes peloric flowers are formed.


dichotoma-717

A first glance this mutant (right) is almost indistinguishable from wild type (left). However there is a gap (arrows), of varying degrees, at the join of the dorsal lobes (in wild type there is an overlap). The gene is important in the control of flower shape and when homozygous as a double mutant with cycloidea gives a combinatorial effect, to form a radially symmetrical (peloric) flower.


radialis-609

Flowers of this mutant are more symmetrical and trumpet-like than that of wild type. The 2 dorsal lobes retain much of their wild type appearence, the 3 ventral lobes all resemble that of the single vental lobe of wild-type but fold down and back towards the corolla tube, to give an overall flattened appearence to the flowers.


Requesting Stocks

Some of these stocks are available for research and teaching purposes . For further information and requests for seed please contact Lucy Copsey. Any request should be accompanied by a brief description of the research to be undertaken.

modified on 17 December 2009 at 10:18 ••• 67,877 views