Abstract
The MADS-domain transcription factor SHORT VEGETATIVE PHASE plays a key role as a repressor of the transition to flowering and as a regulator of early floral development in Arabidopsis thaliana (Arabidopsis). However, no flowering-time repressors have been functionally identified in the model legume Medicago truncatula (Medicago). In this study, phylogenetic analysis of two closely-related MtSVP-like sequences, MtSVP1 and MtSVP2, showed that their predicted proteins clustered together within the eudicot SVP clade. To determine if the MtSVP-like genes have a role in flowering, they were functionally characterized in Medicago and Arabidopsis. Transcripts of both MtSVP genes were abundant and broadly expressed in vegetative tissues but were detected at much lower levels in flowers in Medicago. Over-expression of the MtSVP genes in Arabidopsis resulted in delayed flowering and flowers with many abnormal phenotypes such as leafy sepals, changes to floral organ number and longer pedicels than the wild type. By contrast, in transgenic Medicago, over-expression of MtSVP1 resulted in alterations to flower development, but did not alter flowering time, suggesting that MtSVP1 may not function to repress the transition to flowering in Medicago.
Highlights
Plants precisely regulate the timing of the transition from vegetative to reproductive growth to optimize sexual reproduction and productivity (Putterill et al, 2004)
Alignment with SVP/AGAMOUS-LIKE 24 (AGL24)-like proteins indicates that the MADS-box, intervening (I-box) region, and keratinlike (K-box) motif are well conserved in MtSVP1 and MtSVP2 consistent with the features shared by the MADS-domain family of transcription factors in plants (Parenicova et al, 2003)
In a Neighbor–Joining phylogenetic tree, MtSVP1 and MtSVP2 grouped with eudicot SVP/AGL24 proteins in a clade that is distinct from other Arabidopsis MADS-box proteins such as SUPPRESSOR OF OVER-EXPRESSION OF CONSTANS1 (SOC1), AGL14 and AGL19 (Fig. 1B)
Summary
Plants precisely regulate the timing of the transition from vegetative to reproductive growth to optimize sexual reproduction and productivity (Putterill et al, 2004). In Arabidopsis, six major pathways influence flowering time in response to external (photoperiod, vernalization, and thermosensory pathways) and endogenous signals (autonomous, age, and gibberellin) with carbohydrate status playing a critical role in controlling the transition to flowering (Wahl et al, 2013). Flowering signals from these multiple pathways are integrated by floral integrator genes including FLOWERING LOCUS T (FT), TWIN SISTER OF FT (TSF), and SUPPRESSOR OF OVER-EXPRESSION OF CONSTANS1 (SOC1) that go on to promote the transition to flowering. The expression of AtSVP is down-regulated by the thermosensory, autonomous, and gibberellin floweringtime pathways and after the transition to flowering there is loss of AtSVP expression in the inflorescence meristem (Hartmann et al, 2000; Lee et al, 2007b; Liu et al, 2007; Li et al, 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
