Abstract
In Arabidopsis, AP1 is a floral meristem identity gene and plays an important role in floral organ development. In this study, PsnAP1-1 and PsnAP1-2 were isolated from the male reproductive buds of poplar (Populus simonii × P. nigra), which are the orthologs of AP1 in Arabidopsis, by sequence analysis. Northern blot and qRT-PCR analysis showed that PsnAP1-1 and PsnAP1-2 exhibited high expression level in early inflorescence development of poplar. Subcellular localization showed the PsnAP1-1 and PsnAP1-2 proteins are localized in the nucleus. Overexpression of PsnAP1-1 and PsnAP1-2 in tobacco under the control of a CaMV 35S promoter significantly enhanced early flowering. These transgenic plants also showed much earlier stem initiation and higher rates of photosynthesis than did wild-type tobacco. qRT-PCR analysis further indicated that overexpression of PsnAP1-1 and PsnAP1-2 resulted in up-regulation of genes related to flowering, such as NtMADS4, NtMADS5 and NtMADS11. Overexpression of PsnAP1-1 and PsnAP1-2 in Arabidopsis also induced early flowering, but did not complement the ap1-10 floral morphology to any noticeable extent. This study indicates that PsnAP1-1 and PsnAP1-2 play a role in floral transition of poplar.
Highlights
In Arabidopsis, flowering time is controlled by photoperiod, vernalization, gibberellin, autonomous, and endogenous pathways
Isolation and analysis of the PsnAP1-1 and PsnAP1-2 Two homologous AP1 cDNAs were cloned from poplar male flower buds of P. simonii 6 P. nigra using RT-PCR, and named PsnAP1-1 (GenBank No KC866354) and PsnAP1-2 (GenBank No KC866355)
Genetic and molecular studies in Arabidopsis have led to the identification of over 80 genes involved in the transition from vegetative to reproductive growth, providing a base knowledge for the understanding of floral gene interactions [24]
Summary
In Arabidopsis, flowering time is controlled by photoperiod, vernalization, gibberellin, autonomous, and endogenous pathways. Integrators act upstream of floral meristem identity genes to determine the fate of the shoot apical meristem (SAM) [3]. In Arabidopsis, AP1 is a floral meristem identity gene, and plays an important role in the transition from vegetative to reproductive growth. Transgenic Arabidopsis plants which constitutively express the AP1 gene show transformation of apical and lateral shoots into flowers, and these plants flower much earlier than wild-type plants [4]. Besides being a floral meristem identity gene, AP1 plays an important role in floral organ development in Arabidopsis. Overexpression of MdMADS5, an APETALA1-like gene in apple, caused early flowering in transgenic Arabidopsis [9]. Overexpression of birch BpAP1 in tobacco and birch caused early flowering and dwarfism, giving these plants an obviously shortened juvenile phase [10], [11]
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