Yekti Asih Purwestri

14-3-3 proteins act as intracellular receptors for rice Hd3a florigen

‘Florigen’ was proposed 75 years ago to be synthesized in the leaf and transported to the shoot apex, where it induces flowering. Only recently have genetic and biochemical studies established that florigen is encoded by FLOWERING LOCUS T (FT), a gene that is universally conserved in higher plants. Nonetheless, the exact function of florigen during floral induction remains poorly understood and receptors for florigen have not been identified. Here we show that the rice FT homologue Hd3a interacts with 14-3-3 proteins in the apical cells of shoots, yielding a complex that translocates to the nucleus and binds to the Oryza sativa (Os)FD1 transcription factor, a rice homologue of Arabidopsis thaliana FD. The resultant ternary ‘florigen activation complex’ (FAC) induces transcription of OsMADS15, a homologue of A. thaliana APETALA1 (AP1), which leads to flowering. We have determined the 2.4 Å crystal structure of rice FAC, which provides a mechanistic basis for florigen function in flowering. Our results indicate that 14-3-3 proteins act as intracellular receptors for florigen in shoot apical cells, and offer new approaches to manipulate flowering in various crops and trees.

The 14-3-3 Protein GF14c Acts as a Negative Regulator of Flowering in Rice by Interacting with the Florigen Hd3a

Hd3a and FT proteins have recently been proposed to act as florigens in rice and Arabidopsis, respectively; however, the molecular mechanisms of their function remain to be determined. In this study, we identified GF14c (a 14-3-3 protein) as an Hd3a-interacting protein in a yeast two-hybrid screen. In vitro and in vivo experiments, using a combination of pull-down assays and bimolecular fluorescence complementation, confirmed the interaction between Hd3a and GF14c. Functional analysis using either GF14c overexpression or knockout transgenic rice plants indicated that this interaction plays a role in the regulation of flowering. GF14c-overexpressing plants exhibited a delay in flowering and the knockout mutants displayed early flowering relative to the wild-type plants under short-day conditions. These results suggest that GF14c acts as a negative regulator of flowering by interacting with Hd3a. Since the 14-3-3 protein has been shown to interact with FT protein in tomato and Arabidopsis, our results in rice provide important findings about FT signaling in plants.

Metabolic profiling of endophytic bacteria from Purwoceng (Pimpinella pruatjan Molkend) root and antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa

Recent study on antibiotic produced by endophytic bacteria become emerging to fight against the increasing of drug-resistant bacteria. Twenty eight isolates of endophytic bacteria from Purwoceng (Pimpinella pruatjan Molkend) have been screened for their potential in preventing growth of pathogens, including Staphylococcus aureus and Pseudomonas aeruginosa. In the present study four isolates (GP11, GP12, RP6 and DG1) and another three isolates (GP2, GP14 and DG1) showed the activity to prevent the growth of S. aureus and P. aeruginosa ATCC 27853, respectively. Bioactive compounds were extracted from culture broth using ethyl acetate, followed by Thin layer chromatography (TLC) for metabolic profiling to identify the chemical class of compounds. Taxonomic status of the isolates was determined by BLAST analysis based on 16S rRNA sequences. The result of inhibition zone from 500 mg · mL−1 crude extract DG1, GP11, GP12 and RP6 against S. aureus respectively are 0.78 cm, 1.18 cm, 0.95 cm and 1.2 cm, whereas for...