Protea hybrid ‘Carnival’ (P. compacta x P. neriifolia) expresses multiple copies of a LEAFY homologue involved in floral and vegetative development

Abstract

Proteas are woody perennial plants that develop large, complex inflorescences which are popular as cut flowers. Four paralogous genes with sequence similarity to the meristem identity gene LEAFY (LFY) of Arabidopsis thaliana were identified in the Protea cultivar ‘Carnival’ (Protea compacta x Protea neriifolia). The deduced amino acid sequences of Protea LFY (ProLFY) paralogues displayed highly conserved N- and C-terminal regions comparable to that of other LFY proteins. Paralogous sequences shared 97–99% similarity at nucleotide and deduced amino acid levels. To determine if these ProLFY paralogues are involved in floral transition and development, three paralogues were heterologously expressed in A. thaliana Col-0 wild-type and lfy-2 mutant plants. These three paralogues were chosen as they had the greatest sequence dissimilarities which may suggest a different function. Expression of the ProLFY-WL4 paralogue rescued the low fertility of the lfy-2 mutant by restoring seed yield to wild-type levels, and resulted in the conversion of ‘leaf-like’ inflorescences to flowers with a wild-type appearance. ProLFY-WL4 expression levels during ‘Carnival’ meristem development confirmed a role for this paralogue in inflorescence development. The other two paralogues used in heterologous A. thaliana expression studies, ProLFY-L5 and ProLFY-D1, did not rescue fertility or the abnormal floral phenotype of lfy-2. However, transgenic plants developed either smaller leaves when expressing 35S::ProLFY-L5, or larger leaves when expressing 35S::ProLFY-D1, compared to the non-transgenic lfy-2 plants. Together these results suggest that ProLFY paralogues may be involved in both floral and vegetative development of Protea.