A vegetative line of asparagus (Asparagus officinalis) with a homeotic change in flower development is correlated with a functional deficiency in class-B MADS-box genes

Abstract

SummaryWe describe a vegetative line of asparagus (Asparagus officinalis) that bears flowers with highly altered floral organs. Flower buds in a female line (designated ‘GS#2’) of asparagus ‘Gold Schatz’ develop small tepals that are green in colour. Stamens are not found, but floral organs resembling carpels differentiate at positions where stamens would form. As these features appeared to indicate a homeotic mutant caused by loss of B-function in the ABC genetic model, expression analysis of class-B MADS-box genes was performed. Northern blot analysis revealed that appreciable amounts of transcripts for GLO- and DEF-like gene products were present in immature male and female flower buds of wild-type asparagus, but were lacking in those of ‘GS#2’. Southern blot analysis of genomic DNA showed that there was no difference between ‘GS#2’ and wild-type ‘Gold Schatz’ when probed for DEF- and GLOlike genes.. These results demonstrate that a failure of expression of class-B genes was correlated with aberrant morphology in the floral organs of ‘GS#2’. The stamens of flowers in wild-type female asparagus ceased to grow; however, the floral organs of ‘GS#2’ continued to develop without showing abortion.Thus, the line ‘GS#2’ may provide novel material for further examination of the expression of floral organ identity genes in dioecious plants that have been implicated in the sex-specific abortion of floral organs.