Molecular Genetic Understanding of Photoperiodic Regulation of Flowering Time in Arabidopsis and Soybean

The developmental switch from a vegetative phase to reproduction (flowering) is essential for reproduction success in flowering plants, and the timing of the floral transition is regulated by various environmental factors, among which seasonal day-length changes play a critical role to induce flowering at a season favorable for seed production. The photoperiod pathways are well known to regulate flowering time in diverse plants. Here, we summarize recent progresses on molecular mechanisms underlying the photoperiod control of flowering in the long-day plant Arabidopsis as well as the short-day plant soybean; furthermore, the conservation and diversification of photoperiodic regulation of flowering in these two species are discussed.

Morphoanatomy of Pangasionodon hypopthalmus Reared Under Controlled Photoperiod

Fish morphoanatomy is affected by environmental condition such as photoperiod duration. A research on the effects of shortened photoperiod on the morphoanatomy of Pangasionodon hypopthalmus has been conducted. There were 3 treatments applied, namely, 24 hours dark (24D), 18 hours dark (18D) and natural photoperiod (control). The fish, 8 cm total length (TL) and 4 gr body weight (BW) were reared in circular plastic tanks filled with 100 L freshwater and completed with aerators and circulation pumps, 30 fishes/tank. The fish was reared for 8 weeks and fed with commercial fish feed pellets, twice/day, at satiation. The dark condition was created by placing the tanks under dark tarp tents. Morphoanatomy data were studied by the end of experiment. Results shown that the survival of fish was 100%. The growth of fish reared in 24D and 18D was better, more than 20 cm TL and 85 gr BW, while that of the control was 18 cm TL and 72 gr BW. The condition factor as well as the liver condition of fish in all treatment was not different, it was around 1.2. The liver was reddish brown color, smooth and oily in which hepatosomatic index (HSI) value 0.023 in 24D; 0.027 in 18D and 0.048 in control. The visceralsonatic index (VSI) was 0.090 in 24D; 0.70 in 18D and 0.161 in control. In most of fishes reared in 24D and 18D, the gonad were in the 1st maturity stage (gonadosomatic index; GSI 0.0058 to 0.0068), while the gonad of some control fishes were in the 2nd maturity stage (GSI 0.0080). Data obtained shown that the morphoanatomical data (HSI, VSI and GSI) of the fish reared in lengthened dark were lower, but the growth data (TL and BW) was higher than those of the control, indicated that the fish reared in dark condition may allocated more energy for growing.

Natural variation in GmRAV confers ecological adaptation through photoperiod control of flowering time and maturity in soybean

ABSTRACTPhotoperiod strictly controlled vegetative and reproductive growth stages in soybean. A soybean GmRAV transcription factor containing both AP2 and B3 domains was shown to be a key component of this process. We identified six polymorphisms in GmRAV promoter that showed significant association with flowering time and maturity of soybean in one or multiple environments. Soybean varieties with minor polymorphism exhibited longer growth period contributing to soybean adaptation to lower latitudes. The cis-acting element GT1CONSENSUS motif of GmRAV promoter controlled the growth period and shortened R5-R7 by reducing the expression level of GmRAV in soybean. Three GmRAV-overexpressing (GmRAV-ox) transgenic lines displayed later flowering time and maturity, shorter height and fewer numbers of leaves compared with control plants, and transgenic inhibition of GmRAV (GmRAV-i) soybean displayed earlier flowering time and maturity, and increased plant heights. 163 GmRAV-target genes were determined to be putatively directly bound and transcriptionally regulated by GmRAV by combining the results from the DAP-seq and RNA-seq analyses. Two GmRAV binding motifs [C(A/G/T)A(C)ACAA(G/T)A(C/T)A(G/T)] and [C(T/A)A(C/T) C(T/G)CTG] were identified. GmRAV acting downstream of E3E4 delayed soybean growth period by repressing GmFT5a transcriptional activity to guaranteed both vegetative and reproductive phase long enough to allow necessary energy reserved to be accumulated.

Glyphosate Effect on Nitrogen Fixation and Metabolization in RR Soybean

To evaluate under controlled temperature conditions, nutrition and water supply, the influence of glyphosate on nitrogen fixation capacity in Roundup Ready (RR) soybean, BRS Valiosa Roundup Ready. Commercially available seeds were sown in pots containing vermiculite and washed sand (1:1) and after germination, the seeds were inoculated with Bradyrhizobium sp. and kept in nutrient solution without nitrogen, in greenhouse, with temperature control to 27 ºC without photoperiod control, at UNESP, Ilha Solteira, SP. At the vegetative stage, glyphosate was applied at a concentration of 1.8 mg glyphosate/plant once a week. There were two harvests: after 15-21 days after herbicide application, and at reproductive stage. The chlorophyll content in leaves was analyzed and the organs were separated (leaves, roots and nodules) for extraction and quantitation of nitrogenous compounds, in addition to the enzyme allantoinase activity analysis (in vitro) and nitrogenase activity (in vivo). Nodules were counted and weighted. Means were compared by 5% Tukey’s test. It was observed that the application of glyphosate in RR soybeans moderately affected N fixation and assimilation. There were no drastic metabolic changes for the aminoacids, proteins, chlorophylls and ureides in RR soybean treated with glyphosate.