Role of the UGF protein family during plant development
Zusammenfassung der Projektergebnisse
Plants produce new organs throughout their lives using groups of pluripotent stem cells located at the tips of the shoot and the root, in structures called meristems. The size of the shoot apical meristem (SAM) is tightly controlled by a feedback loop, which involves the homeodomain transcription factor WUSCHEL (WUS) and the CLAVATA (CLV) genes. This regulatory circuit is further finetuned by growth regulators such as metabolic factors and hormones. As part of this work we could show that the FANTASTIC FOUR (FAF) genes (previously UNKNOWN GENE FAMILY, UGF), which comprise a plant specific gene family of four members in Arabidopsis, have the potential to regulate the size of the SAM in Arabidopsis. FAF2and FAF4 are expressed in the organizing center (OC) of the shoot meristem, the site of expression of WUS. Consistent with a regulatory interaction between FAFs and WUS, misexpression experiments indicate that the FAF genes can repress WUS, which ultimately leads to an arrest of meristem growth. The finding that meristematic expression of FAF2 and FAF4 is under negative control by CLV3 further supports the idea that the MFgenes are embedded in the meristematic feedback loop. FAF proteins strongly interact with TRAHALOSE-6-PHOSPAHTE SYNTHASE 1 (TPS1), a key enzyme in trehalose metabolism. In addition, FAF misexpression resulted in increased expression of several TRAHALOSE-6-PHOSPAHTE PHOSPHATASEgenes as determined by micro array analysis. Interestingly, an arrest of meristem growth, similar to the effects seen in FAF misexpressing lines, has also been described for tpsl mutants, suggesting that FAF function is indeed tightly linked with trehlalose metabolism. Finally, FAF proteins interact with BPM proteins that are part of a Cullin3 dependent E3 ubiquitin ligase complex, suggesting that FAF proteins are subject to degradation via the 26S proteasome.
