Genetic variation in four maturity genes affects photoperiod insensitivity and PHYA-regulated post-flowering responses of soybean.

BACKGROUND: Absence of or low sensitivity to photoperiod is necessary for short-day crops, such as rice and soybean, to adapt to high latitudes. Photoperiod insensitivity in soybeans is controlled by two genetic systems and involves three important maturity genes: E1, a repressor for two soybean orthologs of Arabidopsis FLOWERING LOCUS T (GmFT2a and GmFT5a), and E3 and E4, which are phytochrome A genes. To elucidate the diverse mechanisms underlying photoperiod insensitivity in soybean, we assessed the genotypes of four maturity genes (E1 through E4) in early-flowering photoperiod-insensitive cultivars and their association with post-flowering responses. RESULTS: We found two novel dysfunctional alleles in accessions originally considered to have a dominant E3 allele according to known DNA markers. The E3 locus, together with E1 and E4, contained multiple dysfunctional alleles. We identified 15 multi-locus genotypes, which we subdivided into 6 genotypic groups by classifying their alleles by function. Of these, the e1-as/e3/E4 genotypic group required an additional novel gene (different from E1, E3, and E4) to condition photoperiod insensitivity. Despite their common pre-flowering photoperiod insensitivity, accessions with different multi-locus genotypes responded differently to the post-flowering photoperiod. Cultivars carrying E3 or E4 were sensitive to photoperiod for post-flowering characteristics, such as reproductive period and stem growth after flowering. The phytochrome A-regulated expression of the determinate growth habit gene Dt1, an ortholog of Arabidopsis TERMINAL FLOWER1, was involved in the persistence of the vegetative activity at the stem apical meristem of flower-induced plants under long-day conditions. CONCLUSIONS: Diverse genetic mechanisms underlie photoperiod insensitivity in soybean. At least three multi-locus genotypes consisting of various allelic combinations at E1, E3, and E4 conferred pre-flowering photoperiod insensitivity to soybean cultivars but led to different responses to photoperiod during post-flowering vegetative and reproductive development. The phyA genes E3 and E4 are major controllers underlying not only pre-flowering but also post-flowering photoperiod responses. The current findings improve our understanding of genetic diversity in pre-flowering photoperiod insensitivity and mechanisms of post-flowering photoperiod responses in soybean.

Characterization of a novel murine preadipocyte line, AP-18, isolated from subcutaneous tissue: analysis of adipocyte-related gene expressions.

Adipocyte lines are a useful tool for adipocyte research. Recently, a new preadipocyte line designated AP-18 was established from subcutaneous tissue of the C3H/He mouse. In this study, we further characterized AP-18 cells. Adipocyte differentiation was assessed by accumulation of fat droplets stained by Oil Red O. The expression of the preadipocyte- or adipocyte-specific genes and adipocytokine genes was analysed qualitatively by RT-PCR and quantitatively by real-time PCR in comparison with the LM cell, a murine fibroblast line, and the 3T3-L1 cell, respectively. AP-18 cells were fibroblastoid in maintenance culture. After the confluence, fat droplets were accumulated in 50-60% of the cells cultured in the medium alone and in 70-90% of the cells cultured with insulin within 2 to 3 weeks. The fat accumulation was not promoted by the addition of dexamethazone, IBMX (3-isobutyl-1-methylxanthine) or troglitazone in combination with insulin, which were obligatory for differentiation of the 3T3-L1 cell, a murine preadipocyte line. Throughout the differentiation, AP-18 cells expressed Pref-1, LPL, C/EBP beta, C/EBP delta, RXR alpha, C/EBP alpha, PPAR gamma, RXR gamma, aP2, GLUT4, SCD1, UCP2, UCP3, TNFalpha, resistin, leptin, adiponectin and PAI-1 genes, but not the UCP1 gene, indicating that the cell is derived from WAT (white adipose tissue). The time course of these gene expressions was similar to that of 3T3-L1 cells, although the expressions were slower and lower in AP-18 cells. These data indicate that AP-18 cells are preadipocytes originated from WAT and differentiate into adipocytes under more physiological conditions than 3T3-L1 cells. AP-18 may be useful in adipocyte research.