甘蓝型油菜的BR响应及BnBZL2基因的功能分析

对甘蓝型油菜(Brassica napus L.)与拟南芥(Arabidopsis thaliana L.)中保守的油菜素甾醇(Brassinosteroids,BR)信号相关基因进行对比分析,并以甘蓝型油菜品种‘沪油15’为材料,对BR信号通路相关同源基因进行了组织表达分析。结果显示,BR合成基因与信号组分在花和幼嫩种子中表达量更高;低浓度BR处理可以促进幼苗根的生长,高浓度BR处理则起抑制作用; BR合成抑制剂(Brassinozole,BRZ)处理可抑制黑暗条件下幼苗下胚轴的伸长; BR处理可以降低BR合成基因的表达水平,而BRZ处理则相反,表明甘蓝型油菜中BR信号增加能反馈抑制BR的合成。烟草(Nicotiana tabacum L.)瞬时表达实验结果发现,与拟南芥BZR1基因同源的甘蓝型油菜BnBZL2编码蛋白定位在细胞质和细胞核中,BR处理可增加BnBZL2的核定位。蛋白质免疫印迹检测结果显示,BR处理可增加去磷酸化BnBZL2的比例。本研究进一步模拟了拟南芥bzr1-1D功能获得性突变体对BnBZL2蛋白进行点突变(BnBZL2*),并构建载体转化拟南芥,黑暗条件下转基因植株幼苗对BRZ处理不敏感,提示BnBZL2*可提高转基因植株的BR信号水平。本研究结果表明甘蓝型油菜中存在与拟南芥相似且保守的BR信号通路和调控机制。     

Brassinosteroid Signal Transduction: A Mix of Conservation and Novelty

Brassinosteroids (BRs) are a unique class of plant steroids that are structurally similar to animal steroid hormones and play important roles in plant growth and development. Unlike the animal steroids, which bind to classical intracellular steroid receptors that directly modulate gene activities after translocation into the nucleus, the plant steroids rely on transmembrane receptor kinases to activate a phosphorylation cascade to regulate gene expression. Recent genetic and biochemical studies have identified several critical BR signaling components and revealed a striking mechanistic similarity between the plant steroid signaling pathway and several well-studied animal signaling cascades involving a receptor kinase and glycogen synthase kinase 3 (GSK3). A working model for BR signal transduction proposes that BR initiates its signaling pathway by promoting heterodimerization of two transmembrane receptor-like kinases at the cell surface, leading to inhibition of a GSK3 kinase and subsequent stabilization and nuclear accumulation of two GSK3 substrates that regulate BR-responsive genes. Such a simple model provides a framework for continued investigation of molecular mechanism(s) of plant steroid signaling.     

Brassinosteroid signaling regulates phosphate starvation-induced malate secretion in plants

Inorganic phosphate (Pi) is often limited in soils due to precipitation with iron (Fe) and aluminum (Al). To scavenge heterogeneously distributed phosphorus (P) resources, plants have evolved a local Pi signaling pathway that induces malate secretion to solubilize the occluded Fe-P or Al-P oxides. In this study, we show that Pi limitation impaired brassinosteroid signaling and downregulated BRASSINAZOLE-RESISTANT 1 (BZR1) expression in Arabidopsis thaliana. Exogenous 2,4-epibrassinolide treatment or constitutive activation of BZR1 (in the bzr1-D mutant) significantly reduced primary root growth inhibition under Pi-starvation conditions by downregulating ALUMINUM-ACTIVATED MALATE TRANSPORTER 1 (ALMT1) expression and malate secretion. Furthermore, AtBZR1 competitively suppressed the activator effect of SENSITIVITY TO PROTON RHIZOTOXICITY 1 (STOP1) on ALMT1 expression and malate secretion in Nicotiana benthamiana leaves and Arabidopsis. The ratio of nuclear-localized STOP1 and BZR1 determined ALMT1 expression and malate secretion in Arabidopsis. In addition, BZR1-inhibited malate secretion is conserved in rice (Oryza sativa). Our findings provide insight into plant mechanisms for optimizing the secretion of malate, an important carbon resource, to adapt to Pi-deficiency stress.     

Studies on protein content and yield levels in rice

Summary Crosses between low and high protein varieties revealed the dominance of low protein over high protein content. The number of desirable segregants with the double combination of high protein and yield were scored in each generation. The increasing frequency of desirable segregants from the F₂ to the F₃ generation in all the crosses increase the chances of selecting desirable recombinants for propagating improved rice varieties. Hybridisation followed by selection may help in developing varieties with high protein content and superior yield potential.     

XIAO is involved in the control of organ size by contributing to the regulation of signaling and homeostasis of brassinosteroids and cell cycling in rice

Organ size is determined by cell number and size, and involves two fundamental processes: cell proliferation and cell expansion. Although several plant hormones are known to play critical roles in shaping organ size by regulating the cell cycle, it is not known whether brassinosteroids (BRs) are also involved in regulating cell division. Here we identified a rice T-DNA insertion mutant for organ size, referred to as xiao, that displays dwarfism and erect leaves, typical BR-related phenotypes, together with reduced seed setting. XIAO is predicted to encode an LRR kinase. The small stature of the xiao mutant resulted from reduced organ sizes due to decreased cell numbers resulting from reduced cell division rate, as supported by the observed co-expression of XIAO with a number of genes involved in cell cycling. The xiao mutant displayed a tissue-specific enhanced BR response and greatly reduced BR contents at the whole-plant level. These results indicated that XIAO is a regulator of BR signaling and cell division. Thus, XIAO may provide a possible connection between BRs and cell-cycle regulation in controlling organ growth.     

Ligand Perception,Activation, and Early Signaling of Plant Steroid Receptor Brassinosteroid Insensitive

Leucine-rich repeat receptor-like kinases （LRR-RLKs） belong to a large group of cell surface proteins involved in many aspects of plant development and environmental responses in both monocots and dicots. Brassinosteroid insensitive 1 （BRI1）, a member of the LRR X subfamily, was first identified through several forward genetic screenings for mutants insensitive to brassinosteroids （BRs）, which are a class of plant-specific steroid hormones. Since its identification, BRI1 and its homologs had been proved as receptors perceiving BRs and initiating BR signaling. The co-receptor BRIl-associated kinase 1 and its homologs, and other BRI1 interacting proteins such as its inhibitor BRI1 kinase inhibitor I （BKI1） were identified by genetic andbiochemical approaches. The detailed mechanisms of BR perception by BRI1 and the activation of BRI1 receptor complex have also been elucidated. Moreover, several mechanisms for termination of the activated BRI1 signaling were also discovered. In this review, we will focus on the recent advances on the mechanism of BRI1 phosphorylation and activation, the regulation of its receptor complex, the structure basis of BRI1 ectodomain and BR recognition, its direct substrates, and the termination of the activated BRI1 receptor complex.     

施氮水平对两种水稻产量影响的动态模拟及施肥优化分析

借助水稻生长模型ORYZA-0和氮肥管理模块,通过田间和水槽的水稻氮肥试验,对水稻模型和N素动态模块进行了验证。结果表明,模型模拟的不同N素水平水稻生物量、产量同实际测定值明显呈正相关。其中,氮肥用量160kg·hm^-2为最佳经济施氮量,通过获得的水稻参数和氮肥应用曲线模拟的氮肥运筹结果表明：1)在低N(N<100kg·hm^-2)水平下,氮肥应在移栽后35d内全部施入;2)当施氮量为100～200kg·hm^-2时,N应在移栽后45d内全部施入;3)当施氮量N>200kg·hm^-2时,氮肥应在移栽后60d内全部施入;4)随着施氮量的增加,后期施肥比重可略为增加。总体来看,模型不仅能较准确地模拟水稻生长动态,而且可以模拟水稻N吸收和积累的行为动态,从大田晚稻的氮肥运筹模拟结果可看出,氮肥应用次数越多,越接近施氮应用积累曲线的连续施氮产量模拟值(6199kg·hm^-2),但是在实际生产中这会增加农民的用工量和生产成本,难以让农民接受。因而在生产实际中既能让生产者接受,又不致较多地影响产量和收入,在160kg·hm^-2(纯N)施用量下的最佳施肥方案为N素化肥分4次按0．2：0．3：0．3：0．2的比例,分别于移栽后5、20、30和40d施入,可获得5916kg·hm^-2的产量。     

Relative effectiveness of various types and methods of zinc application on rice and maize crops grown in calcareous soil

Summary Application of zinc sulphate mixed with compost/poultry manure proved to be equivalent to the effect of dipping the seedling roots in 4% ZnO suspension with respect to rice yields but Zn-amended organic manures were superior to other treatments with regards to total Zn uptake. A marked residual effect of soil applied treatments was recorded on the succeeding maize crop. Application of poultry manure alone was about one and a half times more effective than compost alone in increasing the rice and maize grain yields. Poultry manure surpassed compost in increasing zinc uptake by the crops and at the same time it built up more available Zn in soil than compost for the following crop. The magnitude of yields and Zn uptake response were magnified when zinc sulphate was applied along with organic manures. Application of 25 kg zinc sulphate/ha alone had the same effect as 50 quintals poultry manure alone or 12.5 kg zinc sulphate applied with 50 quintals compost/ha with respect to crop yields. A significant positive correlation was, recorded in both the crops between Zn concentration in grain or straw and their respective yields.     

Competitive action between Brassinosteroid and tracheary element differentiation inhibitory factor in controlling xylem cell differentiation

For permanent secondary growth in plants, cell proliferation and differentiation should be strictly controlled in the vascular meristem consisting of (pro)cambial cells. A peptide hormone tracheary element differentiation inhibitory factor (TDIF) functions to inhibit xylem differentiation, while a plant hormone brassinosteroid (BR) promotes xylem differentiation in (pro)cambial cells. However, it remains unclear how TDIF and BR cooperate to regulate xylem differentiation for the proper maintenance of the vascular meristem. In this study, I developed an easy evaluation method for xylem differentiation frequency in a vascular induction system Vascular cell Induction culture System Using Arabidopsis Leaves (VISUAL) by utilizing a xylem-specific luciferase reporter line. In this quantitative system, TDIF suppressed and BR promoted xylem differentiation in a dose-dependent manner, respectively. Moreover, simultaneous treatment of TDIF and BR with (pro)cambial cells revealed that they can cancel their each other’s effect on xylem differentiation, suggesting a competitive relationship between TDIF and BR. Thus, mutual inhibition of “ON” and “OFF” signal enables the fine-tuned regulation of xylem differentiation in the vascular meristem.     

油菜素甾醇与IAA对黄化稻二叶切段倾斜效应的比较及相互关系

利用“黄化水稻第二叶切段倾斜法”探讨了BS与IAA对黄化水稻第二叶切段倾斜效应的比较及相互关系。结果显示,两激素都能促进切段倾斜,其效应均被抗IAA运输的TIBA抑制,但切段对BS敏感得多。两激素在这一效应上有协同作用。     

不同水分管理方式下水稻的水分利用效率与产量

采用温室微区试验研究常规水作、裸地旱作、覆膜旱作和覆草旱作等土壤水分管理下水稻生长及其对水分的利用状况。结果表明,几种旱作水稻的需水量为349-473mm,常规水和水稻需水量为762.5mm。旱作水稻的水分籽粒和干物质生产效率为0.899-1.273g·kg^-1和1.655-2.321g·kg^-1之间,而相同条件下常规水作水稻水分的籽粒和干物质生产效率为0.766g·kg^-1和1.459g·kg^-1左右。覆草旱作水稻可以获得相当于常规水作水稻90％的经济产量。     

Functional and signaling mechanism analysis of rice CRYPTOCHROME 1

Cryptochromes (CRY) are blue-light photoreceptors that mediate various light responses, such as inhibition of hypocotyl elongation, enhancement of cotyledon expansion, anthocyanin accumulation and stomatal opening in Arabidopsis. The signaling mechanism of Arabidopsis CRY is mediated through direct interaction with COP1, a negative regulator of photomorphogenesis. CRY has now been characterized in tomato, pea, moss and fern, but its function in monocots is largely unknown. Here we report the function and basic signaling mechanism of rice cryptochrome 1 (OsCRY1). Overexpresion of OsCRY1b resulted in a blue light-dependent short hypcotyl phenotype in Arabidopsis, and a short coleoptile, leaf sheath and leaf blade phenotype in rice (Oryza sativa). On fusion with beta-glucuronidase (GUS), the C-terminal domain of either OsCRY1a (OsCCT1a) or OsCRY1b (OsCCT1b) mediated a constitutive photomorphogenic (COP) phenotype in both Arabidopsis and rice, whereas OsCCT1b mutants corresponding to missense mutations in previously described Arabidopsis cry1 alleles failed to confer a COP phenotype. Yeast two-hybrid and subcellular co-localization studies demonstrated that OsCRY1b interacted physically with rice COP1 (OsCOP1). From these results, we conclude that OsCRY1 is implicated in blue-light inhibition of coleoptile and leaf elongation during early seedling development in rice, and that the signaling mechanism of OsCRY1 involves direct interaction with OsCOP1.     

Function of the {alpha} Subunit of Rice Heterotrimeric G Protein in Brassinosteroid Signaling

The subunit of plant heterotrimeric G proteins (G) plays pivotalroles in multiple aspects of development and responses to planthormones. Recently, several lines of evidence have shown thatG participates in brassinosteroid (BR) responses in Arabidopsisand rice plants. In this study, we conducted a comprehensiveanalysis of the roles of the rice G in the responses to BR usinga defective mutant of the G gene, T65d1. Decreased sensitivityto 24-epi-brassinolide (24-epiBL) in the T65d1 mutant was observedin many processes examined, e.g. in the inhibition of root growthand the promotion of coleoptile elongation. The T65d1 mutantalso showed similar phenotypes to those of BR-deficient mutants,such as the specifically shortened second internode and theconstitutive photomorphogenic growth phenotype under dark conditions.However, a negative feedback effect by 24-epiBL on the expressionof BR biosynthetic genes was observed in the T65d1 mutant, andthe levels of BR intermediates did not fluctuate in this mutant.To determine the epistatic relationship between the T65d1 mutantand d61-7, a weak allele of a rice BR receptor mutant, the twomutants were crossed. The T65d1/d61-7 double mutant showed noepistasis in the elongation inhibition of the internodes, theinternode elongation pattern, the leaf angle and the morphologicalabnormality of leaf, except for the vertical length of seedand the seed weight. Our results suggest that the rice G affectsthe BR signaling cascade but the G may not be a signaling moleculein BRI1-meditated perception/transduction.     

开放式空气CO2浓度增高对水稻产量形成的影响

在大田栽培条件下 ,研究开放式空气CO2 浓度增加 (FACE) 2 0 0 μmol·mol-1的处理对水稻产量及产量构成因素的影响 .结果表明 ,FACE处理对水稻株高和主茎叶片数没有明显影响 ,但使水稻生育进程加快 ,全生育期显著缩短 ,增加施N量可减缓FACE处理对水稻全生育期缩短的程度 ;FACE处理能显著增加分蘖数 ,极显著增加穗数 ,提高结实率 ,但使每穗颖花数显著减少 ;FACE处理能显著提高水稻产量 ,在高N条件下增产幅度更大 ;提高FACE处理的每穗颖花数和单位面积颖花数能极显著提高水稻产量 ,增加施N量是提高FACE处理每穗颖花数和单位面积颖花数的重要措施 .     

Effects of deep placement and surface application of urea on the yield of wetland rice in pot trials

Summary The effects of deep placement and surface application of urea fertilizer on the yield of rice grown in pots of alluvial clay soil covered with 5 cm water was studied under controlled conditions. Application of two levels of urea supergranules and prills (2 g and 4 g urea/0.1 m²) on the surface of submerged soil increased the vegetative growth and enhanced the grain yield as much as 85%. However, no difference in yield was found between urea prills applied in three split doses and one application of urea supergranules.Deep placement of two levels of urea supergranules in the soil at four different depths (2.5, 5.0, 10.0 and 15.0 cm) resulted in the highest yields. The fertilizer was most efficient when the highest concentration was placed in the soil at a depth of 5.0 cm. This application method increased the grain yield by 20% as compared with the soil surface application.