Epsilon Open Archive

Abstract

Flower development progress through distinct phases that are controlled by complex genetic networks, which in turn are regulated by both endogenous and exogenous factors. A large number of functional studies have been conducted over the past decades to understand the genetic networks that regulate flower development in angiosperm model species. In gymnosperms, however, the gene regulatory networks behind distinct phases of cone development are largely unknown due to the lack of functional studies.

In a morphological study of early cone development in Picea abies, three distinct growth phases were defined. Transcriptome comparisons of female and vegetative buds in the three growth phases identified members of the MADS-box gene family, LEAFY-orthologs, bZIP- , AP2-, and SBP-domain proteins as being highly expressed in the different phases of female cone development. In a separate study different isoform of the MADS-box gene, DAL19 were identified. Isoforms specific expression in male, female and vegetative bud meristems provided evidence that alternative splicing may influence cone formation in a bud identity specific manner.

In the early cone-setting acrocona mutant, P. abies var. acrocona, leading shoots often have needles at the base, but ovuliferous scale-like structures in the top. Hence, during shoot development, the leading shoots make a morphological shift and produce transition shoots. RNA sequencing of acrocona transition shoots demonstrated that the MADS-box genes DAL10 and DAL21, which previously have been associated with reproductive shoot identity were expressed at high levels in transition shoot meristems before the morphological shift. In addition, genes encoding FT/TFL-like, bZIP-, SOC1-like and gymnosperm specific MADS-domain proteins co-expressed with DAL10 and DAL21, suggesting at a putative role for these genes in the early development of reproductive meristems. In addition, genes encoding F-box protein and ubiquitin were expressed at high levels in late acrocona transition shoots, which possibly reflects an involvement of hormonal signalling in the acrocona transition shoot phenotype.