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The apelin gene can promote vascular endothelial cell (VEC) proliferation, migration, and angiogenesis. However, the molecular mechanism for regulation of the apelin gene is still unknown. Real-time PCR and Western blotting analysis were employed to detect the effect of all-trans retinoic acid (ATRA) in up-regulating apelin expression in human umbilical vein endothelial cells (HUVECs). Furthermore, the in vivo study also indicated that ATRA could increase apelin expression in balloon-injured arteries of rats, which is consistent with the results from the cultured HUVECs. To ensure whether retinoic acid receptor (RAR) α (RARα) could be induced by ATRA in regulating apelin, the expression of RARα was tested with a siRNA method to knock down RARα or adenovirus vector infection to overexpress RARα. The results showed that ATRA could up-regulate apelin expression time- and dose- dependently in HUVECs. ATRA could induce a RARα increase; however, the expression of RARβ and RARγ were unchanged. The blocking of RARα signaling reduced the response of apelin to ATRA when HUVECs were treated with RARα antagonists (Ro 41-5253) or the use of siRNA against RARα (si-RARα) knockdown RARα expression before using ATRA. In addition, induction of RARα overexpression by infection with pAd-GFP-RARα further increased the induction of apelin by ATRA. These results suggested that ATRA up-regulated apelin expression by promoting RARα signaling.

WRINKLED1 (WRI1) belongs to AP2/EREBP transcription factor. Its function in dicots for fatty acids synthesis has been deeply studied, but its role in monocot, especially in rice, is still poorly understood. Here, with the overexpression of AtWRI1 in rice, we found its overexpression increased fatty acids content in vegetative organs and seed coat including aleurone layer (SCAL) but decreased fatty acids content in endosperm. Meanwhile, the overexpression of AtWRI1 increased starch content in endosperm. These results provide a new insight into the function of AtWRI1in monocot and make a previous basement for the study of the connection of fatty acids and starch synthesis in rice.

In this study, we investigated how printed sowing machine transplanting impacts the yield of single-season rice by increasing the planting density and decreasing the amount of fertilizer needed. The study was aimed at exploring the relationships between the amount of fertilizer, transplanting density, and rice yield. During the rice growing season from 2019 to 2020 in the middle and lower reaches of the Yangtze River, six different field trials were conducted: low density and high fertilizer (LDHF), low density and low fertilizer (LDLF), middle density and high fertilizer (MDHF), middle density and low fertilizer (MDLF), high density and high fertilizer (HDHF), and high density and low fertilizer (HDLF). It turns out that compared to the LDHF, the thousand seed weight, the spikelets per panicle, the seed-setting rate, and the SPAD value at the filling stage decreased by 0.17% and 0.60%, 5.36% and 10.59%, 5.70% and 4.66%, and 17.52% and 4.93% in 2019 and 2020, respectively. However, compared to the LDHF, the panicles increased by 15.31% and 17.18%, respectively, the LAI at the filling stage increased by 1.92% and 0.48%, respectively, and the accumulation of dry matter above ground at the maturity stage also increased by 3.74% and 16.79% in 2019 and 2020, respectively. Therefore, compared to the yield of rice in the LDHF, the yield of rice in the HDLF increased by 5.06% and 6.64%. The yields of rice in the LDLF, MDHF, MDLF, and HDHF were lower than that in the LDHF and HDLF. The partial least squares path model (PLSPM) analysis showed that the fertilizer, density, and aboveground dry matter had positive effects on the yield, while the SPAD value and LAI had negative effects on the yield. This research shows that increasing the transplanting density can compensate for the yield loss caused by reducing the fertilizer amount. However, no combination of the transplanting density and fertilization amount can achieve the purpose of increasing the yield.

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