Water deficit, leaf rolling and susceptibility to photoinhibition in field grown sorghum

Chlorophyll fluorescence and gas-exchange techniques were used to investigate changes in photosynthelic performance in response to high light and mild water deficit, in two cultivars of the C., plant sorghum ( Sorghurn bicofor [L.] Moench). grown under field conditions. For all leaves fully exposed to the sun, the efficiency of phcttosystem 11 (PSII) showed a mid-day decline, hut with substantial over-night recovery: the magnitude of the mid-day decline was enhanced by water deficit. There was no corresponding decline in leaves not exposed to full sunlight, either because they were shaded by other leaves or else because of leaf-roiling. Net assimilation rates appeared more sensitive to water-deficit than was PSI1 efficiency. Shade-adapted leaves had lower rates of photosynthesis in full sun (and lower stomatal conductances) than well-exposed leaves. When these shade-adapted leaves were suddenly exposed to full sunlight, fluorescence quenching was slow. especially when plants were well-watered. For the latter, photochemical quenching (q_p)was small even after several minutes. indicating a continuing imbalance between energy funnelled to PSI1 and subsequent electron transport. Shade-adapted leaves that were water stressed were better able to withstand a sudden increase in irradiance than those that were well watered. It is suggested that the shade-adapted eaves from unirrigated plants. having a lower s'tomatal conductance than the irrigated leaves, had been acclimated by receiving energy in excess of that required to fix CO₂, thus leading to the operation of dissipative mechanisms. A shortened protocol for quenching analysis is proposed that enables non-photochemical quenching to be partitioned into rapidly and slowly relaxing components (the latter including photoinhibition) by relating results to a theoretical maximum yield of variable fluorescence. This is particularly suitable for screening field material.     

高梁CRY2基因的克隆及其表达分析

从高粱(Sorghum bicolor L. var.R1ll)幼苗中提取总RNA,利用RT-PCR和cDNA的3'末端的快速扩增方法(3'RACE),第一次克隆了高粱隐花色素2基因(CRY2)的cDNA序列.该序列包括了一个完整的开放阅读框,编码大小为690个氨基酸残基的蛋白质,与水稻、番茄和拟南芥CRY2蛋白质的同源性分别为8 7%、5 7%和45.5%.高粱CRY2基因组DNA含有3个内含子和4个外显子.RT-PCR检测结果表明,高粱CRY2基因在根、茎和叶中都有转录.Western blotting结果显示CRY2蛋白在根、茎和叶中表达,并在黑暗中积累,蓝光下降解.高粱CRY2可能在蓝光诱导的幼苗去黄化反应中起作用.     

高粱CRY2基因的克隆及其表达分析

从高粱(Sorghum bicolor L．var．R111)幼苗中提取总RNA,利用RT-PCR和cDNA的3′末端的快速扩增方法(3′RACE),第一次克隆了高粱隐花色素2基因(CRY2)的cDNA序列。该序列包括了一个完整的开放阅读框,编码大小为690个氨基酸残基的蛋白质,与水稻、番茄和拟南芥CRY2蛋白质的同源性分别为87％、57％和45．5％。高粱CRY2基因组DNA含有3个内含子和4个外显子。RT-PCR检测结果表明,高粱CRY2基因在根、茎和叶中都有转录。Western blotting结果显示CRY2蛋白在根、茎和叶中表达,并在黑暗中积累,蓝光下降解。高粱CRY2可能在蓝光诱导的幼苗去黄化反应中起作用。     

高粱可溶性酸性转化酶基因(SAI-1)PCR克隆方法

可溶性酸性转化酶(SAI)是蔗糖代谢途径中的关键酶,对植物生长发育起着至关重要的调节作用,研究简捷快速克隆可溶性酸性转化酶基因方法,对于育种材料和品种资源的基因分型具有重要意义。本研究通过已知的高粱可溶性酸性转化酶基因序列及高粱基因组中该基因序列片段,设计引物,比较了分段克隆、基因全长克隆、巢式PCR克隆等方法克隆高粱SAI-1基因的效果,结果表明,直接扩增全长,扩增产物极其不稳定且扩增产物纯化、连接,转化后得不到阳性克隆;采用均等分段克隆,前半段扩增产物纯化、连接转化后得不到阳性克隆,但后半段克隆成功;针对高粱基因组信息中SAI-1基因上游的未知序列部分设计引物,进行单独克隆(635 bp),再单独克隆其其余序列,两段序列拼接后得到SAI-1基因全长。序列分析发现,SAI-1前段635 bp的扩增片段GC含量高达69.6%,而其后GC含量急剧下降至30%以下,所以推测全长克隆、均等片段克隆以及巢式PCR克隆失败的原因可能是SAI-1基因中GC分布不均匀,克隆高粱SAI-1基因较为适宜的方法为利用2对引物进行不均等分段扩增克隆,前段PCR退火温度较后段高1℃。该方法将为其他研究人员提供有益参考。     

高粱SPL基因家族的鉴定及表达分析

Squamosa启动子结合类蛋白(SPL)基因家族编码一类植物特有的转录因子,其功能涉及作物遗传改良的许多方面,如产量、株型、抗逆性等,具有重要的实际应用价值。虽然SPL基因在很多作物中有广泛研究,但是在高粱中仍有待进一步探索。本研究通过生物信息学方法,利用同源序列法在高粱基因组水平对SPL基因家族进行分离和分析,共获得19个高粱SPL基因,并命名为SbSPL。高粱SbSPL家族基因不均匀地分布于高粱9条染色体上。通过系统进化树、保守结构域和基因结构等分析,将SbSPL基因家族成员分为5组,不同组的SbSPL基因在功能结构上具有保守性。此外,分析了SbSPL基因家族成员的启动子,发现SbSPL基因家族具有响应非生物胁迫相关信号转导的顺式作用元件。利用qRT-PCR技术,发现部分高粱SbSPL基因的表达受干旱胁迫诱导。这些结果揭示了SbSPL基因可能在高粱响应环境非生物胁迫过程中起到重要作用。     

Infrared Spectroscopy of Some Mannans

Bacterial production of 4-hydroxy(3,4-d)pyrazolopyrirnidine riboside (AP–R) was studied. Seven among 73 tested strains were found to produce AP–R through N-ribosyl transfer reaction between uridine and 4-hydroxy(3,4-d)pyrazolopyrimidine (allopurinol). AP–R was produced by the cell-free extract of Erwinia carotovora and was isolated in crystals from the reaction mixture. The crystalline AP–R was characterized by spectroscopic data and was confirmed to be β-1-ribosyl allopurinol. AP–R could not substitute for inosine to support the growth of a nonexacting purine base-requiring mutant of Sarcina lutea.     

高粱SBP-box基因家族全基因组鉴定及表达分析

SQUAMOSA PROMOTER BINDING PROTEIN box (SBP-box)基因家族编码一类绿色植物特有的转录因子,其功能涉及作物遗传改良的许多方面,如产量、株型、抗逆性等,具有重要的实际应用价值。本研究通过生物信息学方法从高粱(Sorghum bicolor L.)全基因组中鉴定出18个SBP-box基因,分布于9条染色体上,其中8个基因位于基因组重复区域。系统发育分析表明高粱SBP-box基因家族可分为6个亚家族,其中SbSBP12、SbSBP3和SbSBP15分别与玉米ZmLG1、ZmTGA1和ZmUB2/3直系同源。基于RNA-seq数据的表达分析发现高粱SBP-box基因在花序原基中表达量最高,SbSBP9和SbSBP17为花序原基特异表达基因,SbSBP5、SbSBP8和SbSBP18等基因受外源ABA和PEG胁迫上调表达,表明SBP-box基因可能参与高粱对非生物逆境的响应。本研究为高粱SBP-box家族重要基因的克隆提供了参考,相关基因可作为高粱遗传改良的候选基因。     

Cloning of a Novel Rat Gene, DB83, That Encodes a Putative Membrane Protein

Using a partial cDNA sequence and a 5'-RACE technique, we isolateda novel cDNA from rat liver referred to as DB83. DB83 had fourhydrophobic trans-membrane domains and one N-myristoylationsite as well as multiple possible phosphorylation sites. Thedb83 gene was highly expressed in the liver and significantlyin brain, lungs and kidneys. We suggest that DB83 is a tissue-specificputative membrane protein.     

Genetic transformation of Sorghum bicolor

Great millet (Sorghum bicolor (L.) Moench) is cultivated across the world for food and fodder. It is typically grown in semiarid regions that are not suitable for cultivation of other major cereals. Sexual incompatibility and shortage of available genes in germplasm to combat biotic and abiotic stresses resulted in marginalized yields of this crop. Genetic modification of sorghum with agronomically useful genes can address this problem. Here, we tried to review and summarize the key aspects of sorghum transformation work being carried out so far by various research groups across the world. The approaches used and the obstacles in generating transgenic sorghum are also pointed out and discussed.     

脱水蛋白研究进展

植物在干旱胁迫下会产生许多逆境响应蛋白,其中最常见的是脱水蛋白(dehydrin).脱水蛋白具有高度保守的序列.根据近年研究的进展对脱水蛋白的功能和基因表达调控规律作了简要的综述.     

载脂蛋白E3的克隆及原核表达

载脂蛋白Ｅ(ａｐｏｌｉｐｏｐｒｏｔｅｉｎＥ ,ａｐｏＥ)由 2 99个氨基酸组成 ,分子量 34ｋＤ ,是维持人体正常脂质代谢的必需蛋白质 .它是乳糜微粒 (ＣＭ )、极低密度脂蛋白 (ＶＬＤＬ)和高密度脂蛋白 (ＨＤＬ)的组分 ,是极低密度脂蛋白受体的重要配体 ,是脂质进入细胞不可缺少的中介 .ａｐｏＥ有 3种同分异构体 :ａｐｏＥ2、ａｐｏＥ3、ａｐｏＥ4 ,分别具有不同的生理作用 .ａｐｏＥ4与血浆高胆固醇、心血管疾病和老年痴呆等疾病关联[1～ 3 ] .ａｐｏＥ2与Ⅲ型高脂血症有关 ,并对老年痴呆有防治作用[4,5] .ａｐｏＥ3是大多数健康人所具有…     

mRNA levels of four tomato (Lycopersicon esculentum Mill. L.) genes related to fluctuating plant and soil water status

Expression of the genes le20, ni3212, le25 and lcyp2 was quantified in relation to soil and plant water status for pot-grown tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig) in a replicated trial in a partially environmentally controlled glasshouse. Leaf water potential, relative water content, stomatal conductance and gravimetric soil water content were measured at 0800,1200 and 1600 h on three days during the imposition of three different watering regimes. Paired leaf samples were analysed for mRNA. Plant-to-plant variability was quantified and partitioned. le20 mRNA was found in all leaves and responded both to short-term diurnal fluctuations in water status and to more severe stress, though with reduced sensitivity to the greatest stresses. An overnight decline in le20 mRNA was independent of soil or plant water status. The pattern of expression for ni3212 was similar though ni3212 mRNA was much more abundant and the overnight drop in expression was not significant. le25 mRNA was only detected where leaf water potential was below ?0.9 MPa and increased linearly with further decline in leaf water potential. lcyp2 was constitutively expressed with a diurnal pattern characterized by a sharp depression at 1600 h but with expression being enhanced by increasing water deficit at all times. The control and significance of the four genes are discussed in relation to the proposed function of their respective gene products.     

Regulation of gene expression by endogenous ABA in tomato plants

In response to water deficit, endogenous abscisic acid (ABA) accumulates in plants. This ABA serves as a signal for a multitude of processes, including regulation of gene expression. ABA accumulated in response to water deficit signals cellular as well as whole plant responses playing a role in the pattern of gene expression throughout the plant. Although the function of genes regulated by ABA during stress are currently poorly understood, a number of these genes may permit the plant to adapt to environmental stress.