BOTRYOID POLLEN 1 regulates ROS-triggered PCD and pollen wall development by controlling UDP-sugar homeostasis in rice.

Uridine diphosphate (UDP)-sugars are important metabolites involved in the biosynthesis of polysaccharides and may be important signaling molecules. UDP-glucose 4-epimerase (UGE) catalyzes the interconversion between UDP-Glc and UDP-Gal, whose biological function in rice (Oryza sativa) fertility is poorly understood. Here, we identify and characterize the botryoid pollen 1 (bp1) mutant and show that BP1 encodes a UGE that regulates UDP-sugar homeostasis, thereby controlling the development of rice anthers. The loss of BP1 function led to massive accumulation of UDP-Glc and imbalance of other UDP-sugars. We determined that the higher levels of UDP-Glc and its derivatives in bp1 may induce the expression of NADPH oxidase genes, resulting in a premature accumulation of reactive oxygen species (ROS), thereby advancing programmed cell death (PCD) of anther walls but delaying the end of tapetal degradation. The accumulation of UDP-Glc as metabolites resulted in an abnormal degradation of callose, producing an adhesive microspore. Furthermore, the UDP-sugar metabolism pathway is not only involved in the formation of intine but also in the formation of the initial framework for extine. Our results reveal how UDP-sugars regulate anther development and provide new clues for cellular ROS accumulation and PCD triggered by UDP-Glc as a signaling molecule.

Methylesterification of cell-wall pectin controls the diurnal flower-opening times in rice.

Flowers are the core reproductive organ of plants, and flowering is essential for cross-pollination. Diurnal flower-opening time is thus a key trait influencing reproductive isolation, hybrid breeding, and thermostability in plants. However, the molecular mechanisms controlling this trait remain unknown. Here, we report that rice Diurnal Flower Opening Time 1 (DFOT1) modulates pectin methylesterase (PME) activity to regulate pectin methylesterification levels of the lodicule cell walls, which affect lodicule swelling to control diurnal flower-opening time. DFOT1 is specifically expressed in the lodicules, and its expression gradually increases with the approach to flowering but decreases with flowering. Importantly, a knockout of DFOT1 showed earlier diurnal flower opening. We demonstrate that DFOT1 interacts directly with multiple PMEs to promote their activity. Knockout of PME40 also resulted in early diurnal flower opening, whereas overexpression of PME42 delayed diurnal flower opening. Lower PME activity was observed to be associated with higher levels of pectin methylesterification and the softening of cell walls in lodicules, which contribute to the absorption of water by lodicules and cause them to swell, thus promoting early diurnal flower opening. Higher PME activity had the opposite effect. Collectively, our work uncovers a molecular mechanism underlying the regulation of diurnal flower-opening time in rice, which would help reduce the costs of hybrid breeding and improve the heat tolerance of flowering plants by avoiding higher temperatures at anthesis.

Anti-hyperuricemic and nephroprotective effects of Rhizoma Dioscoreae septemlobae extracts and its main component dioscin via regulation of mOAT1, mURAT1 and mOCT2 in hypertensive mice.

Rhizoma Dioscoreae septemlobae (RDSE) has been widely used for the treatment of hyperuricemia in China. However, the therapeutic mechanism has been unknown. This study investigated the antihyperuricemic mechanisms of the extracts obtained from RDSE and its main component dioscin (DIS) in hyperuricemic mice. Hyperuricemic mice were induced by potassium oxonate (250 mg/kg). RDSE or DIS was orally administered to hyperuricemic mice at dosages of 319.22, 638.43, 1276.86 mg/kg/day for 10 days, respectively. Uric acid or creatinine in serum and urine was determined by HPLC or HPLC-MS/MS, respectively. The xanthine oxidase (XO) activities in mice liver were examined in vitro. Protein levels of organic anion transporter 1 (mOAT1), urate transporter 1 (mURAT1) and organic cation transporter 2 (mOCT2) in the kidney were analyzed by western blotting. The results indicated that uric acid and creatinine in serum were significantly increased by potassium oxonate, as compared to that of control mice. Compared saline-treated group, after RDSE treatment in the high and middle dose, the expression of mOAT1 increased 47.98 and 54.48 %, respectively, which accompanied with the decreased expression of mURAT1 (47.63 %) in high dose. After DIS treatment in high, middle and low dose, the expression of mOAT1 increased 23.93, 32.80 and 25.28 % compared to saline-treated group, respectively, which accompanied with the decreased expression of mURAT1 (51.07, 51.42 and 51.35 %). However, RDSE and DIS displayed a weak XO inhibition activity compared with allopurinol. Therefore, RDSE and DIS processed uricosuric and nephroprotective actions by regulation of mOAT1, mURAT1 and mOCT2.

[Study on effect of fushenkeli on expression of TAK1 in human renal tubular epithelial cells and its possible mechanism].

OBJECTIVE: To investigate the effects of fushenkeli on the expression of TAK1 in the proliferation of the renal tubular epithelial cells induced by TGF-beta1 and its possible mechanism. METHOD: Human renal tubular epithelial (HK-2) cells were divided into five groups:blank control group, TGF-beta1 group (5 microg x L(-1)), intervention group 1 (5 microg x L(-1) of TGF-beta1 + 100 mg x L(-1) of fushenkeli), intervention group 2 (5 microg x L(-1) of TGF-beta1 + 500 mg x L(-1) of fushenkeli) and intervention group 3 (5 microg x L(-1) of TGF-beta1 + 1 g x L(-1) of fushenkeli). HK-2 proliferation was detected by methyl thiazolyl tetrazolium (MTT) assay. Type IV collagen in the supernatants of the cultured HK-2 was detected by ELISA at 12, 24, 48 hours respectively. The protein and mRNA expressions of TAK1 was measured by Western blot and real-time quantitative PCR. RESULT: 1) The cell proliferation and the expression of type IV collagen were increased compared with the control group (P<0.05, P<0.01), but they were decreased in intervention group. 2) The expressions of protein and mRNA of TAK1 in TGF-beta1 group were upregulating significantly compared with control group (P<0.01), but they were downregulating in intervention group, especially in intervention group 3. CONCLUSION: Fushenkeli could inhibits TAK1 expression induced by TGF-beta1 in the proliferation of HK-2 cell.