Effects of rising temperatures and [CO2] on the physiology of tropical forest trees

Using a mixture of observations and climate model outputs and a simple parametrization of leaf-level photosynthesis incorporating known temperature sensitivities, we find no evidence for tropical forests currently existing ‘dangerously close’ to their optimum temperature range. Our model suggests that although reductions in photosynthetic rate at leaf temperatures (TL) above 30°C may occur, these are almost entirely accountable for in terms of reductions in stomatal conductance in response to higher leaf-to-air vapour pressure deficits D. This is as opposed to direct effects of TL on photosynthetic metabolism. We also find that increases in photosynthetic rates associated with increases in ambient [CO2] over forthcoming decades should more than offset any decline in photosynthetic productivity due to higher D or TL or increased autotrophic respiration rates as a consequence of higher tissue temperatures. We also find little direct evidence that tropical forests should not be able to respond to increases in [CO2] and argue that the magnitude and pattern of increases in forest dynamics across Amazonia observed over the last few decades are consistent with a [CO2]-induced stimulation of tree growth

Molecular and physiological responses during thermal acclimation of leaf photosynthesis and respiration in rice

To further our understanding of how sustained changes in temperature affect the carbon economy of rice (Oryza sativa), hydroponically grown plants of the IR64 cultivar were developed at 30°C/25°C (day/night) before being shifted to 25/20°C or 40/35°C. Leaf messenger RNA and protein abundance, sugar and starch concentrations, and gas‐exchange and elongation rates were measured on preexisting leaves (PE) already developed at 30/25°C or leaves newly developed (ND) subsequent to temperature transfer. Following a shift in growth temperature, there was a transient adjustment in metabolic gene transcript abundance of PE leaves before homoeostasis was reached within 24 hr, aligning with Rdark (leaf dark respiratory CO2 release) and An (net CO2 assimilation) changes. With longer exposure, the central respiratory protein cytochrome c oxidase (COX) declined in abundance at 40/35°C. In contrast to Rdark, An was maintained across the three growth temperatures in ND leaves. Soluble sugars did not differ significantly with growth temperature, and growth was fastest with extended exposure at 40/35°C. The results highlight that acclimation of photosynthesis and respiration is asynchronous in rice, with heat‐acclimated plants exhibiting a striking ability to maintain net carbon gain and growth when exposed to heat‐wave temperatures, even while reducing investment in energy‐conserving respiratory pathways.Peer reviewe

Increasing water-use efficiency directly through genetic manipulation of stomatal density

Improvement in crop water-use efficiency (WUE) is a critical priority for regions facing increased drought or diminished groundwater resources. Despite new tools for the manipulation of stomatal development, the engineering of plants with high WUE remains a challenge. We used Arabidopsis epidermal patterning factor (EPF) mutants exhibiting altered stomatal density to test whether WUE could be improved directly by manipulation of the genes controlling stomatal density. Specifically, we tested whether constitutive overexpression of EPF2 reduced stomatal density and maximum stomatal conductance (gw(max)) sufficiently to increase WUE. We found that a reduction in gw(max) via reduced stomatal density in EPF2-overexpressing plants (EPF2OE) increased both instantaneous and long-term WUE without altering significantly the photosynthetic capacity. Conversely, plants lacking both EPF1 and EPF2 expression (epf1epf2) exhibited higher stomatal density, higher gw(max) and lower instantaneous WUE, as well as lower (but not significantly so) long-term WUE. Targeted genetic modification of stomatal conductance, such as in EPF2OE, is a viable approach for the engineering of higher WUE in crops, particularly in future high-carbon-dioxide (CO2) atmospheres

STAT3 gain-of-function mutations connect leukemia with autoimmune disease by pathological NKG2Dhi CD8+T cell dysregulation and accumulation

The association between cancer and autoimmune disease is unexplained, exemplified by T cell large granular lymphocytic leukemia (T-LGL) where gain-of-function (GOF) somatic STAT3 mutations correlate with co -exist-ing autoimmunity. To investigate whether these mutations are the cause or consequence of CD8+ T cell clonal expansions and autoimmunity, we analyzed patients and mice with germline STAT3 GOF mutations. STAT3 GOF mutations drove the accumulation of effector CD8+ T cell clones highly expressing NKG2D, the receptor for stress-induced MHC-class-I-related molecules. This subset also expressed genes for granzymes, perforin, interferon-y, and Ccl5/Rantes and required NKG2D and the IL-15/IL-2 receptor IL2RB for maximal accumula-tion. Leukocyte-restricted STAT3 GOF was sufficient and CD8+ T cells were essential for lethal pathology in mice. These results demonstrate that STAT3 GOF mutations cause effector CD8+ T cell oligoclonal accumu-lation and that these rogue cells contribute to autoimmune pathology, supporting the hypothesis that somatic mutations in leukemia/lymphoma driver genes contribute to autoimmune disease.Peer reviewe

Role of the Arabidopsis PIN6 auxin transporter in auxin homeostasis and auxin-mediated development

Plant-specific PIN-formed (PIN) efflux transporters for the plant hormone auxin are required for tissue-specific directional auxin transport and cellular auxin homeostasis. The Arabidopsis PIN protein family has been shown to play important roles in developmental processes such as embryogenesis, organogenesis, vascular tissue differentiation, root meristem patterning and tropic growth. Here we analyzed roles of the less characterised Arabidopsis PIN6 auxin transporter. PIN6 is auxin-inducible and is expressed during multiple auxin–regulated developmental processes. Loss of pin6 function interfered with primary root growth and lateral root development. Misexpression of PIN6 affected auxin transport and interfered with auxin homeostasis in other growth processes such as shoot apical dominance, lateral root primordia development, adventitious root formation, root hair outgrowth and root waving. These changes in auxin-regulated growth correlated with a reduction in total auxin transport as well as with an altered activity of DR5-GUS auxin response reporter. Overall, the data indicate that PIN6 regulates auxin homeostasis during plant development.Christopher I. Cazzonelli, Marleen Vanstraelen, Sibu Simon, Kuide Yin, Ashley Carron-Arthur, Nazia Nisar, Gauri Tarle, Abby J. Cuttriss¤, Iain R. Searle, Eva Benkova, Ulrike Mathesius, Josette Masle, Jiří Friml, Barry J. Pogso

The College News, 1923-01-24, Vol. 09, No. 13

Bryn Mawr College student newspaper. Merged with The Haverford News in 1968 to form the Bi-college News (with various titles from 1968 on). Published weekly (except holidays) during the academic year

Physicochemical characterization of must and wine Moscato Giallo from grapevines grown under plastic overhead cover

O objetivo deste trabalho foi avaliar a influência da cobertura de plástico sobre as características físico-químicas do mosto e do vinho da cultivar Moscato Giallo. Na safra 2006, um experimento em delineamento completamente casualizado foi realizado em vinhedo com cobertura de plástico impermeável, e sem cobertura como controle. De cada vinhedo, três microvinificações (20 L) foram elaboradas. Foram realizadas avaliações físico-químicas quanto ao: mosto – oBrix, açúcares redutores, densidade, acidez total, ácido tartárico, ácido málico e pH; e vinho – densidade, graduação alcoólica, acidez total, acidez volátil, pH, extrato seco, açúcares redutores, cinzas, I 420, compostos voláteis e minerais. O mosto das videiras cobertas apresentou maior rendimento, porém, menor concentração de açúcares pelo fato de a maturação das uvas ter-se atrasado. Como conseqüência, os vinhos do cultivo protegido tiveram menor graduação alcoólica, embora tenham sido beneficiados pela sanidade das uvas, com a redução de acetato de etila e acidez volátil. O microclima da cobertura também restringiu a concentração de alguns minerais no vinho, principalmente P e K. A cobertura beneficiou a qualidade enológica, porém requer atraso na data de colheita, para as uvas atingirem adequada maturação fisiológica e tecnológica.The objective of this work was to evaluate the plastic overhead cover (POC) effect on must and wine composition of the cultivar Moscato Giallo. In 2006 vintage, it was performed a completely randomly designed experiment, in a vineyard covered with an impermeable plastic cloth, and without covering as control. From each vineyard, three microvinification (20 L) were elaborated. Physico-chemical analysis were performed for: musts – oBrix, reducer sugar contents, density, total acidity, tartaric acid, malic acid and pH; and wines – density, alcohol degree, acidity, volatile acidity, pH, dry extract, reducer sugar contents, ashes, I 420, volatile compounds and minerals. The must of the covered vineyard presented higher yield, but lower sugar content, due to delay on ripening. As consequence, the POC wines showed lower alcohol degree, but with the benefit of a lower ethyl-acetate and volatile acidity levels. The POC microclimate also caused a decrease of some minerals (mainly P and K) in the wines. POC improved the enological quality, however, this demands delay in the harvest date to achieve the adequate physiological and technological maturation of grapes

Integrated physical, genetic and genome map of chickpea (Cicer arietinum L.)

Physical map of chickpea was developed for the reference chickpea genotype (ICC 4958) using bacterial artificial chromosome (BAC) libraries targeting 71,094 clones (~12× coverage). High information content fingerprinting (HICF) of these clones gave high-quality fingerprinting data for 67,483 clones, and 1,174 contigs comprising 46,112 clones and 3,256 singletons were defined. In brief, 574 Mb genome size was assembled in 1,174 contigs with an average of 0.49 Mb per contig and 3,256 singletons represent 407 Mb genome. The physical map was linked with two genetic maps with the help of 245 BAC-end sequence (BES)-derived simple sequence repeat (SSR) markers. This allowed locating some of the BACs in the vicinity of some important quantitative trait loci (QTLs) for drought tolerance and reistance to Fusarium wilt and Ascochyta blight. In addition, fingerprinted contig (FPC) assembly was also integrated with the draft genome sequence of chickpea. As a result, ~965 BACs including 163 minimum tilling path (MTP) clones could be mapped on eight pseudo-molecules of chickpea forming 491 hypothetical contigs representing 54,013,992 bp (~54 Mb) of the draft genome. Comprehensive analysis of markers in abiotic and biotic stress tolerance QTL regions led to identification of 654, 306 and 23 genes in drought tolerance “QTL-hotspot” region, Ascochyta blight resistance QTL region and Fusarium wilt resistance QTL region, respectively. Integrated physical, genetic and genome map should provide a foundation for cloning and isolation of QTLs/genes for molecular dissection of traits as well as markers for molecular breeding for chickpea improvement