Trade-offs between light interception and leaf water shedding: a comparison of shade- and sun-adapted species in a subtropical rainforest

Species in high-rainfall regions have two major alternative approaches to quickly drain off water, i.e., increasing leaf inclination angles relative to the horizontal plane, or developing long leaf drip tips. We hypothesized that shade-adapted species will have more pronounced leaf drip tips but not greater inclination angles (which can reduce the ability to intercept light) compared to sun-adapted species and that length of leaf drip tips will be negatively correlated with photosynthetic capacity [characterized by light-saturated net photosynthetic rates (A _max), associated light compensation points (LCP), and light saturation points (LSP)]. We tested this hypothesis by measuring morphological and physiological traits that are associated with light-interception and water shedding for seven shade-adapted shrub species, ten sun-adapted understory shrub species, and 15 sun-adapted tree species in a subtropical Chinese rainforest, where mean annual precipitation is around 1,600 mm. Shade-adapted understory species had lower LMA, A _max, LSP, and LCP compared to understory or canopy sun-adapted species; their leaf and twig inclination angles were significantly smaller and leaf drip tips were significantly longer than those in sun-adapted species. This suggests that shade-adapted understory species tend to develop pronounced leaf drip tips but not large leaf inclination angles to shed water. The length of leaf drip tips was negatively correlated with leaf inclination angles and photosynthetic capacity. These relationships were consistent between ordinary regression and phylogenetic generalized least squares analyses. Our study illustrates the trade-offs between light interception and leaf water shedding and indicates that length of leaf drip tips can be used as an indicator of adaptation to shady conditions and overall photosynthetic performance of shrub species in subtropical rainforests.     

Identification and mapping of a novel blackleg resistance locus LepR4 in the progenies from Brassica napus × B. rapa subsp. sylvestris

Blackleg, caused by Leptosphaeria maculans, is one of the most economically important diseases of Brassica napus worldwide. Two blackleg-resistant lines, 16S and 61446, were developed through interspecific hybridization between B. napus and B. rapa subsp. sylvestris and backcrossing to B. napus. Classical genetic analysis demonstrated that a single recessive gene in both lines conferred resistance to L. maculans and that the resistance alleles were allelic. Using BC₁ progeny derived from each resistant plant, this locus was mapped to B. napus linkage group N6 and was flanked by microsatellite markers sN2189b and sORH72a in an interval of about 10 cM, in a region equivalent to about 6 Mb of B. rapa DNA sequence. This new resistance gene locus was designated as LepR4. The two lines were evaluated for resistance to a wide range of L. maculans isolates using cotyledon inoculation tests under controlled environment conditions, and for stem canker resistance in blackleg field nurseries. Results indicated that line 16S, carrying LepR4a, was highly resistant to all isolates tested on cotyledons and had a high level of stem canker resistance under field conditions. Line 61446, carrying LepR4b, was only resistant to some of the isolates tested on cotyledons and was weakly resistant to stem canker under field conditions.     

An ultradense genetic recombination map for <Emphasis Type="Italic">Brassica napus</Emphasis>, consisting of 13551 SRAP markers

Sequence related amplified polymorphism (SRAP) was used to construct an ultradense genetic recombination map for a doubled haploid (DH) population in B. napus. A total of 1,634 primer combinations including 12 fluorescently labeled primers and 442 unlabeled ones produced 13,551 mapped SRAP markers. All these SRAPs were assembled in 1,055 bins that were placed onto 19 linkage groups. Ten of the nineteen linkage groups were assigned to the A genome and the remaining nine to the C genome on the basis of the differential SRAP PCR amplification in two DH lines of B. rapa and B. oleracea. Furthermore, all 19 linkage groups were assigned to their corresponding N1–N19 groups of B. napus by comparison with 55 SSR markers used to construct previous maps in this species. In total, 1,663 crossovers were detected, resulting in a map length span of 1604.8 cM. The marker density is 8.45 SRAPs per cM, and there could be more than one marker in 100 kb physical distance. There are four linkage groups in the A genome with more than 800 SRAP markers each, and three linkage groups in the C genome with more 1,000 SRAP markers each. Our studies suggest that a single SRAP map might be applicable to the three Brassica species, B. napus, B. oleracea and B. rapa. The use of this ultra high-density genetic recombination map in marker development and map-based gene cloning is discussed. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

人参茎叶皂甙对创伤小鼠活化T细胞内磷脂酰肌醇代谢的影响

研究了人参茎叶皂甙（ＧＳＬ）对创伤小鼠活化Ｔ细胞内磷脂酰肌醇代谢的影响。结果显示,ＧＳＬ体内应用（５０ｍｇ·ｋｇ￣（－１）·ｄ￣（－１）,伤后０─３ｄ）对创伤小鼠活化Ｔ细胞内三磷酸肌醇（ＩＰ＿３）、游离Ｃａ￣（２＋）、钙调素（ＣａＭ）、ＣａＭ依赖的蛋白激酶（ＣａＭ－Ｐｋ）、蛋白激酶Ｃ（ＰＫＣ）水平的降低具有明显的逆转效应,并可明显降低创伤小鼠血清、巨噬细胞、Ｔｓ细胞对各指标的抑制活性。ＧＳＬ（１．０─１００ｍｇ／Ｌ）在体外也可明显提高创伤小鼠活化Ｔ细胞内ＩＰ＿３、Ｃａ￣（２＋）、ＣａＭ、ＣａＭ－ＰＫ及ＰＫＣ水平。上述结果表明,ＧＳＬ可逆转创伤小鼠活化Ｔ细胞内磷脂酰肌醇代谢的降低。     

小麦幼胚培养再生植株第二代（R2）抗赤霉病性的遗传分析

本文从赤霉病抗扩展各过程,研究了小麦幼胚再生植株R_2代的抗性表现。R_2代抗性具有数量性状的遗传特点,较之F_2代,R_2代更具有发病慢、病情轻、抗扩展能力增强、发病速度上株系间差异显著等特点,并有可能出现低频率的高抗植株,这些高抗植株将是有用的抗源。     

创伤后抑制性T细胞对活化T细胞内白介素2及白介素2受体α基因表达的影响

研究了创伤小鼠抑制性T细胞(Ts)对白介素2(IL-2)及IL-2受体(IL-2R)α基因表达的抑制作用。结果表明,创伤后Ts细胞对正常活化T细胞内IL-2 mRNA及IL-2 RαmRNA水平的抑制作用增强,以伤后4天最为明显,伤后10天仍未恢复正常。创伤后Ts细胞还可升高正常活化T细胞内cAMP含量,降低cGMP含量,增加cAMP/cGMP比值。且可降低三磷酸肌醇(IP_3)含量、游离钙(Ca~(2 ))浓度、钙调素(CaM)、钙调素依赖性蛋白激酶(CaM-PK)及蛋白激酶C(PKC)的活性。去除创伤小鼠活化T细胞中的Ts细胞,则可使其IL-2mRNA及IL-2RαmRNA水平明显升高。并可使cAMP、cGMP、IP_3含量、Ca~(2 )浓度、CaM、CaM-PK及PKC活性的变化发生逆转。表明创伤后Ts细胞可通过影响T细胞内环核苷酸含量及磷脂酰肌醇代谢途径,进而抑制IL-2及IL-2 Rα的基因表达。