菜薹叶片衰老相关转录因子BrWRKY75的特性分析

以菜薹[Brassica rapa L. ssp. chinensis（L.）Mokino var. utilis Tsen et Lee]为材料,克隆得到1个WRKY转录因子,命名为BrWRKY75。氨基酸序列比对及进化树分析发现BrWRKY75与拟南芥的WRKY75同源性较高,且同属于第Ⅱ类c亚族。实时荧光定量PCR表明BrWRKY75在菜薹叶片衰老过程中表达明显增强。亚细胞定位和转录活性分析显示BrWRKY75定位于细胞核,是一种核蛋白,并且具有转录抑制活性。体外凝胶阻滞试验（EMSA）证实BrWRKY75能与W-box（TTGAC）元件特异结合。上述结果为进一步研究菜薹叶片衰老的转录调控机制奠定了基础。     

Correlation of Leaf and Root Senescence During Ripening in Dry Seeded and Transplanted Rice

Dry seeding is a resource-saving rice establishment method. With an equivalent yield, dry seeded flooded rice (DSR) has been considered as a replacement for traditional transplanted flooded rice (TFR). However, the differences in leaf and root senescence during grain filling between DSR and TFR were seldom identified. In this study, the root length, root tip number and leaf senescence of rice varieties Huanghuazhan and Yangliangyou 6 during ripening were compared between DSR and TFR. Results showed that top three leaves in DSR had the characteristics of relatively lower SPAD value, lower N content and premature leaf senescence. In addition, both the total root length and total root tip number of DSR were significantly lower than those of TFR. In conclusion, premature and quick leaf senescence was related with inadequate root length and root tip number during ripening, which might result from the deficiency of nitrogen supply in DSR. Techniques on improving leaf nitrogen status and delaying the leaf senescence during grain-filling in DSR should be developed in future researches.     

Differential regulation of senescence and in vitro differentiation by 17β-estradiol between mesenchymal stem cells derived from male and female mini-pigs

The characterization and potential of mesenchymal stem cells (MSCs) are gender dependent and estrogen influences these properties. This study demonstrated that supplementation with 17β-estradiol (E2) increases the proliferation of bone marrow-MSCs derived from male and female mini-pigs (Mp- and Fp-BMSCs) in a concentration-dependent manner, with 10^-12 M E2 suggested as the optimal dose of E2 that led to the greatest improvement in BMSCs proliferation. Supplementation of 10^-12 M E2 resulted in down-regulation of β-galactosidase activity and pro-apoptotic activity in both BMSCs, while anti-apoptotic activity was up-regulated in only Fp-BMSCs. Further, E2 increased the osteogenic ability of Fp-BMSCs. Based on these findings, optimal utilization of E2 can improve cellular senescence and apoptosis, as well as in vitro osteogenesis of BMSCs, and could therefore be useful in stem cell therapy, particularly in bone regeneration for adult females.     

Deep Roots are Pivotal for Regulating Post‐Anthesis Leaf Senescence in Wheat (Triticum aestivum L.)

Root activity plays a dominant role in grain filling in cereal crops. However, the importance of deep roots for regulating post‐anthesis leaf senescence is not clearly understood in wheat (Triticum aestivum L.). In this study, we used ³²P tracing to estimate the difference in wheat root activity at soil depths of 30 and 70 cm and the root restriction method to investigate the effects of vertical distribution of deep roots on leaf senescence, with non‐restricted plants as controls. Recovery of radioactive ³²P indicated that deep roots had significantly higher activity than upper roots in wheat. Root restriction at a soil depth of 50 cm caused significant decreases in the activities of superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6) and ascorbate peroxidase (EC 1.11.1.11) at 16 days after anthesis and thereafter resulting in an increase in malondialdehyde. As a result, chlorophyll levels and net photosynthesis decreased. Ultimately, the root‐restricted wheat produced a significantly lower grain yield than the non‐restricted controls. These data suggest that deep roots are pivotal for regulating plant senescence, duration of grain filling, and yield formation.     

Knock-down of EZH2 expression promotes senescence of ovarian cancer cells

AIM: To investigate the molecular mechanism of down-regulated EZH2 expression promoting senescence of ovarian cancer cells. METHODS: Real- time PCR, Western blot and immunohistochemistry were used to detect the expression of EZH2 in ovarian cancer tissues, normal tissues, 4 ovarian cancer cell lines and IOSE80 cells. The ovarian cancer cells and IOSE80 cells were transfected with EZH2 siRNA (siEZH2) by Lipofectamine 2000 or treated with GSK126. Transfected IOSE80 cells were treated with ionizing radiation for 72 h, and negative control siRNA served as a control. The cell proliferation, apoptotic rate and senescence were detected by MTT assay, colony formation assay, flow cytometry and SA-β-Gal staining. The protein levels of EZH2, p53, p21, p16, caspase-3, cleaved caspase-3, PARP, cleaved PARP, H3K27me3, H3K27me2 and H3K27me1 were determined by Western blot. RESULTS: The EZH2 expression in the ovarian cancer tissues and ovarian cancer cells was significantly higher than that in the normal tissues and IOSE80 cells, respectively (P<0.01). siEZH2 significantly inhibited the proliferation of ovarian cancer cells, and promoted ionizing radiation-induced senescence. This effect was consistent with the cell phenotype after GSK126 treatment. Knock-down of EZH2 expression significantly inhibited the expression of H3K27me3, promoted the expression of p53, p21 and p16 (P<0.01), and had no effect on the protein levels of the key molecules in the apoptotic pathway. CONCLUSION: EZH2 is highly expressed in ovarian cancer tissues and ovarian cancer cells. Knock-down of EZH2 expression promotes the senescence of ovarian cancer cells via decrease in H3K27me3 level, thus inhibiting the proliferation of the cells.     

Differential Physio‐Biochemical Responses to Cold Stress of Cold‐Tolerant and Non‐Tolerant Grapes (Vitis L.) from China

There are many grape species exhibiting differences in cold tolerance in China. ‘Zuoshan1’ (Vitis amurensis Rupr. cv. Zuoshan1), one kind of the most cold tolerant grapes, can endure ?40 to ?50 °C, whereas, ‘Maoputao’ (Vitis quinqanguoari Rehd. cv. Maoputao) is sensitive to the cold stress. To understand the physiological mechanism, we investigated responses of both species to a range of decreasing temperatures under the controlled condition. The cold‐tolerant ‘Zuoshan1’ showed higher accumulation of abscisic acid than non‐tolerant ‘Maoputao’, which was correlated with a more dramatic increase in solutes including sugars, proteins at early stage of our detection. At latter stages, these solutes showed more decline in ‘Zuoshan1’. Meanwhile, earlier leaf yellowing and necrosis of ‘Zuoshan1’ were detected with concomitant decrease in the chlorophyll (Chl) content along with remarkable increase in electrolyte leakage and malondialdehyde, which indicated that the earlier leaf senescence occurred to ‘Zuoshan1’. Based on the leaf morphology and parameter investigation, it was concluded that cold‐tolerant grape ‘Zuoshan1’ made quicker responses to the low temperature (LT), indicating it sensed the cold‐signal more strongly than the non‐tolerant grape ‘Maoputao’. Therefore the ability to take more active response to cold stress contributes to the higher tolerance in ‘Zuoshan1’.     

Weakened carbon and nitrogen metabolisms under post-silking heat stress reduce the yield and dry matter accumulation in waxy maize

Post-silking high temperature is one of the abiotic factors that affects waxy maize(Zea mays L. sinensis Kulesh) growth in southern China. We conducted a pot trial in 2016–2017 to study the effects of post-silking daytime heat stress(35°C) on the activities of enzymes involved in leaf carbon and nitrogen metabolisms and leaf reactive oxygen species(ROS) and water contents. This study could improve our understanding on dry matter accumulation and translocation and grain yield production. Results indicated that decreased grain number and weight under heat stress led to yield loss, which decreased by 20.8 and 20.0% in 2016 and 2017, respectively. High temperature reduced post-silking dry matter accumulation(16.1 and 29.5% in 2016 and 2017, respectively) and promoted translocation of pre-silking photoassimilates stored in vegetative organs, especially in leaf. The lower leaf water content and chlorophyll SPAD value, and higher ROS(H_2O_2 and O_2~-·) content under heat stress conditions indicated accelerated senescent rate. The weak activities of phosphoenolpyruvate carboxylase(PEPCase), Ribulose-1,5-bisphosphate carboxylase(Ru BPCase), nitrate reductase(NR), and glutamine synthase(GS) indicated that leaf carbon and nitrogen metabolisms were suppressed when the plants suffered from a high temperature during grain filling. Correlation analysis results indicated that the reduced grain yield was mainly caused by the decreased leaf water content, weakened NR activity, and increased H_2O_2 content. The increased accumulation of grain weight and post-silking dry matter and the reduced translocation amount in leaf was mainly due to the increased chlorophyll SPAD value and NR activity. Reduced PEPCase and Ru BPCase activities did not affect dry matter accumulation and translocation and grain yield. In conclusion, post-silking heat stress down-regulated the leaf NR and GS activities, increased the leafwater loss rate, increased ROS generation, and induced pre-silking carbohydrate translocation. However, it reduced the post-silking direct photoassimilate deposition, ultimately, leading to grain yield loss.     

不同抚育措施对衰老火炬树叶片生理的影响

通过探讨除萌蘖、修剪、断根3种抚育措施处理对12年生衰老火炬树生理特性的影响，探究其衰老机理。设置4组处理，CK为对照组，D1为除萌蘖处理组，将主树2 m范围内萌蘖苗全部剪除，之后每隔15 d将新萌蘖苗剪除；D2为修剪处理组，将冗杂枝、干枯枝、过密枝疏除，树冠回缩；D3为断根处理组，距树干50 cm处画圆，沿弧线分6段，每隔1段断根处理，共断1/2的根。于6月开始取成熟叶片为试验材料，之后每隔30 d取样1次，测定各处理下叶片的生理指标变化规律。结果表明，在除萌蘖、修剪、断根3种抚育措施处理下，火炬树叶片叶绿素含量、SOD、POD、CAT活性、可溶性蛋白含量呈现 “先升高后降低”的变化趋势，最高值分别较CK显著增长44.78%、22.10%、73.27%、141.31%、39.05%，可溶性糖含量呈现“升高”趋势，MDA含量呈现“先降低后升高”趋势，最低值显著低于CK 25.20%。3种抚育措施处理对火炬树早期预防衰老以及衰老期改善生长状态、延缓火炬树衰老均有明显作用，各处理综合评价结果为除萌蘖处理对衰老火炬树叶片生理影响效果最好，断根处理次之，修剪处理影响效果最差。     

北京市戒台寺、潭柘寺古树衰老的几个生理特征研究

通过对北京市戒台寺和潭柘寺的卧龙松、自在松、抱塔松、活动松等油松、九龙松(白皮松)、娑罗树(七叶树东西两棵)等古树的树体温度、叶绿素含量、树叶及土壤矿物质含量等生理参数进行测定,并与40年生的油松、白皮松、七叶树生长正常的植株进行比较,得出如下结论：(1)树木的衰弱程度与其树体温度有一定相关性,即越衰老的树木树体温度越高;(2)老树叶片的叶绿素含量一般均比健壮植株低;(3)衰老古树呈现明显的缺素症状。