Search | Site Map | Contact

Research: Current Picture

Much work has been done over many years and laboratories into the genetic regulation of flowering, and the state of knowledge at the beginning of the SYSFLO project is summarised in figure 1 (for further details, please see references, full gene names are listed in Table 1 ).

Floral organ identity genes function in different combinations to specify the identity of each type of floral organ: stamens are specified by a combination of AG/AP3/PI/SEP, while carpel development is promoted by AG/SEP. Upstream of the homeotic genes are flowering genes, which control the transition from vegetative to reproductive development. This includes SVP and FUL, which have antagonistic roles in the regulation of key regulators of the initiation of flower development (AP1/SEP, LFY). Downstream of homeotic genes are general regulators of organ growth (e.g. JAG, TCP genes) and genes that control the development of subsets of the tissues and structures within developing organs (SHP1, SHP2, STK). These in turn activate genes with more specific roles in ovule development (REM20, REM37). Several of the genes in this network have roles in multiple developmental steps, for example AP1 controls both floral meristem identity and organ identity (in this case, sepals and petals), while AG, SHP1 and SHP2 function initially during carpel development and subsequently control ovule development, together with STK.

Fig 1. The regulatory network for flower development in Arabidopsis. Boxes contain the genes involved in the indicated developmental steps and shows how they interact genetically with each other and in some cases, biochemically, as in the formation of multi-protein complexes containing different combinations of organ identity and SEP proteins. Arrows and blunted lines represent activation and repression, respectively; dashed lines with question marks indicate predicted interactions. The full names of genes are listed in Table 1 below.

Figure 1

Table 1: Genes involved in Arabidopsis floral development

AG AGAMOUS
AP1 APETALA 1
FUL FRUITFULL
LFY LEAFY
JAG JAGGED
PI PISTILLATA
REM20 REPRODUCTIVE MERISTEM 20
REM37 REPRODUCTIVE MERISTEM 37
SEP SEPALLATA
SHP1 SHATTERPROOF 1
SHP2 SHATTERPROOF 2
SOC1 SUPPRESSOR OF OVEREXPRESSION OF CO 1
STK SEEDSTICK
SVP SHORT VEGETATIVE PHASE
TCP Family of plant specific transcription factors, the name comes from the first members to be identified (Teosinte branched, Cycloidea and PCF1 and 2).
References

[1] Espinosa-Soto et al. (2004). Plant Cell 16, 2923-2939
[2] Gomez-Mena et al. (2005). Dev. 132, 429-438
[3] Wellmer et al. (2006) PLoS Genetics 2, ell7

" Sibel Kabayel