Phosphorus is one of the macronutrients essential for plant growth and development, as well as crop productivity. Many soils around the world are deficient in phosphate (Pi) that plants can utilize. To cope with the stress of Pi starvation, plants have evolved many adaptive strategies, such as changes of root architecture and enhanced Pi acquisition form soil. To understand molecular mechanism underlying Pi starvation stress signaling, we characterized the activation-tagged mutant showing altered responses to Pi deficiency compared to wild type Arabidopsis and named hsp3 (hypersensitive to Pi starvation3). hsp3 mutant exhibits enhanced phosphate transporter activity, resulting in higher Pi content than wild type. However, in root architectural change under Pi starvation, hsp3 shows hyposensitive responses than wild type, such as longer primary root elongation, lower lateral root density. Histochemical analysis using hsp3 mutant expressing auxin-responsive DR5::GUS reporter gene, indicated that auxin allocation from primary to lateral roots under Pi starvation is aborted in hsp3 mutant. Molecular genetic analysis of hsp3 mutant revealed that the mutant phenotype is caused by the lesion in ENHANCED SILENCING PHENOTYPE4 (ESP4) gene whose function is proposed in mRNA 3’ end processing. Here, we propose that mRNA processing plays a crucial role in Pi homeostasis in Arabidopsis.

FLOWERING LOCUS T (FT) is major determinant of the length of the vegetative phase in plants. To understand the role of FT homologs in flowering time control of soybean, we identified ten soybean FT genes and named GmFTs. Expression analysis of GmFT homologs showed that the transcripts of most FT clade genes are mainly expressed in leaves. The expression of GmFT2a, GmFT2b, GmFT5a, and GmFT6 strongly induced in response to floral inductive short-day condition, but GmFT4 and GmFT6 exhibited opposite expression pattern. To understand the biological function of each GmFT/TFL1 genes in flowering time control, we ectopically expressed GmFT cDNAs in Arabidopsis under the control of CaMV 35S promoter. Interestingly, while 35S:GmFT2a and 35S:GmFT5a transgenic plant showed extremely early flowering phenotype, overexpression of GmFT4 delayed flowering. Furthermore we analyzed expression patterns GmFT genes in the leaves of Korean soybean landraces showing various flowering time. The results showed that the transcript level of two FT homologs, GmFT2a and GmFT5a, was high in early flowering landraces, but low in late flowering landraces. In contrast, GmFT4 exhibited opposite expression pattern to those of GmFT2a and GmFT5a, suggesting that GmFT4 may function antagonistically to GmFT2a and GmFT5a in flowering time control of soybean. These results demonstrated that soybean FT homologs have both unique and conserved functions in the photoperiodic control of flowering compared with those in Arabidopsis.