POLARBEAR is a Cosmic Microwave Background radiation (CMB) polarization experiment that is located in the Atacama Desert in Chile. The scientific goals of the experiment are to characterize the ...B-mode signal from gravitational lensing, as well as to search for B-mode signals created by primordial gravitational waves (PGWs). Polarbear started observations in 2012 and has published a series of results. These include the first measurement of a nonzero B-mode angular auto-power spectrum at sub-degree scales where the dominant signal is gravitational lensing of the CMB. In addition, we have achieved the first measurement of crosscorrelation between the lensing potential, which was reconstructed from the CMB polarization data alone by Polarbear, and the cosmic shear field from galaxy shapes by the Subaru Hyper Suprime-Cam (HSC) survey. In 2014, we installed a continuously rotating half-wave plate (CRHWP) at the focus of the primary mirror to search for PGWs and demonstrated the control of low-frequency noise. We have found that the low-frequency B-mode power in the combined dataset with the Planck high-frequency maps is consistent with Galactic dust foreground, thus placing an upper limit on the tensor-to-scalar ratio of r < 0.90 at the 95% confidence level after marginalizing over the foregrounds.
Cystatins are protein inhibitors of cystein proteinases belonging to the papain family. In cowpea, cystatin-like polypeptides and a cDNA have been identified from seeds and metabolic functions have ...been attributed to them. This paper describes
VuC1, a new cystatin cDNA isolated from cowpea leaves (
Vigna unguiculata (L.) Walp.). Sequence analysis revealed a multicystatin structure with two cystatin-like domains. The recombinant VUC1 protein (rVUC1) was expressed in an heterologous expression system and purified to apparent homogeneity. It appeared to be an efficient inhibitor of papain activity on a chromogenic substrate. Polyclonal antibodies against rVUC1 were obtained. Involvement of the
VuC1 cDNA in the cellular response to various abiotic stresses (progressive drought-stress, dessication and application of exogenous abscissic acid) was studied, using Northern blot and Western blot analysis, in the leaf tissues of cowpea plants corresponding to two cultivars with different capacity to tolerate drought-stress. Surprisingly, these abiotic stresses induced accumulation of two
VuC1-like messages both translated into VUC1-like polypeptides. Difference in the transcript accumulation patterns was observed between the two cultivars and related to their respective tolerance level. Presence of multiple cystatin-like polypeptides and their possible involvement in the control of leaf protein degradation by cysteine proteinases is discussed.
Relatively little ecophysiological research has been conducted to determine the responses to drought of
Phaseolus vulgaris. Four bean cultivars (cvs.) from Brazil, A320, Carioca, Ouro Negro and Xodó ...were submitted to an imposed water deficit in order to evaluate the importance of some adaptive mechanisms of drought resistance through the analysis of growth parameters, water status, gas exchange and indicators of tolerance mechanisms at the cellular level. During the drought treatment, relative growth rates were more reduced for A320 and Xodó than Carioca and Ouro Negro. A320 closed its stomata very rapidly and complete stomatal closure was obtained at
Ψ
w=−0.6 MPa, in contrast to the other cvs. where stomata were fully closed only at
Ψ
w=−0.9 MPa. Net assimilation rates were closely related to stomatal conductances. Mechanisms at the cellular level appeared to be mostly important for higher tolerance. Carioca and Ouro Negro, when compared to A320 and Xodó, were characterized by having better drought tolerance mechanisms and higher tissue water retention capacity leading to a better growth under water deficits. The leaf dehydration rates of those cvs. were slow whereas those of the drought sensitive cvs. were rapid. The results were confirmed by the electrolyte leakage test and leaf osmotic potential measurements, which indicated higher membrane resistance and osmotic adjustment in the two tolerant cvs. Carioca and Ouro Negro. It appears from this study that despite being cultivated in the same geographical region, the four cvs. of
P. vulgaris displayed somewhat different drought adaptive capacities for prolonged drought during the vegetative phase.
A method was designed to optimize rapid and high frequency direct shoot regeneration (without intermediate callus) of the commercially important common bean,
Phaseolus vulgaris L., using the ...transverse thin cell layer (tTCL) method. The pretreatment of seeds with 10 μM TDZ significantly increased bud regeneration frequency on tTCL. A 2-week culture of tTCLs on 10 μM TDZ followed by a reduction in the TDZ concentration (1 μM) was needed to achieve optimal bud induction and further development of the neo-formed buds. An incubation period greater than 2 weeks of tTCLs with 10 μM TDZ concentration resulted in inhibitory effects on the development of shoots and roots. Shoot development was enhanced by 10 μM BAP and 10 μM AgNO
3 leading to 100% well developed shoots. Regenerated plants developed into true-to-type fertile plants.
A simple protocol was established for high frequency direct shoot regeneration of cowpea
Vigna unguiculata (L.) cv. EPACE-1. Bud proliferation occurred at the cotyledonary nodes of cowpea seedlings ...three weeks after culture on a medium containing Murashige and Skoog salts (1962) and B5 vitamins (Gamborg et al. 1968) supplemented with TDZ. A 10 μmol/L TDZ pre-treatment, shoot tip removal and excision of longitudinal thin cell layers (TCL) at the level of the cotyledonary nodes with subsequent culture on a MSB5 medium supplemented with 1 μmol/L IBA and 1 μmol/L TDZ were the optimal conditions for maximum bud proliferation. Up to 32.5 regenerated shoot buds were produced per TCL. The regenerated plants (R
0) were true-to-type and successfully transferred to soil.
In leaf discs of
Vigna unguiculata cv. EPACE-1 subjected to osmotic stress (PEG MW 8000, −1.3 MPa) a significant decrease in membrane integrity occurred, as evaluated by electrolyte efflux. This ...effect was significantly reduced when discs were treated with ABA (0.1 mM in Tris buffer) prior to PEG treatment. In PEG-treated discs, membrane lipids were drastically degraded, particularly the galactolipids. The percentage of linolenic acid in MGDG also decreased significantly. An ABA pretreatment of discs before osmotic stress significantly decreased galactolipid degradation and preserved their linolenic acid content. We concluded that ABA had a protective effect on membranes against osmotic stress, as attested by electrolyte leakage test and polar lipid analysis. Some possible roles for exogenous ABA in the acquisition of such an enhanced capacity to maintain membrane integrity under dehydration conditions are suggested.
The dehydration tolerance of leaf membranes of three coconut palm (
Cocos nucifera L.) cultivars with different levels of resistance to drought stress in the field was evaluated by analysis of ...membrane lipids. Young plants, grown singly in pots, were subjected to controlled dehydration by witholding watering. The composition of coconut leaf lipids was similar to that of higher plants of the so-called ‘18:3 (α-linolenic)’ group, although the total lipid content was lower than that of herbaceous tropical crops. In response to drought stress, leaf total lipid and chloroplastic major lipid (monogalactosyl diacylglycerol) contents decreased more markedly in the more drought-susceptible cultivars. Analysis of leaf lipids is thus proposed as an early screening test for tolerance to drought stress. Despite the decrease in lipid contents, no modification of the fatty acid composition of total lipid extract and of monogalactosyl diacylglycerol was revealed, suggesting a high membrane tolerance to desiccation in
Cocos. The fatty acid composition of the major phospholipid (phosphatidylcholine) was markedly enriched in α-linolenic acid in response to water deficit, suggesting a slowing down of monogalactosyl diacylglycerol biosynthesis and/or an adaptation to drought stress.
With the aim of selecting physiological tests for the screening of drought tolerant species, we have studied the behaviour of bean leaf discs treated with PEG 600 (−1.13 MPa) for 4 h. The kinetics of ...electrolyte and Pi leakages and of soluble sugar and starch content were studied during 24 h rehydration of the leaf discs. These four tests were related, respectively, to cell and chloroplast membrane integrity and to photosynthetic or sugar mobilization ability. The results obtained showed that stress caused by PEG induced an increase in the leakage of electrolyte of 4 to 7 times and of Pi up to 10 and 28 times, and a decrease in soluble sugar and starch content. These phenomena were stimulated by darkness. The magnitude of the physiological responses varied according to the species but correlated well with each other. Therefore, the tests used are indicators of cell and membrane integrity and they allowed us to propose a classification of the species according to their cell sensitivity to water deficit. The sequence obtained was: Phaseolus vulgaris, sensitive, Phaseolus acutifolius and Vigna radiata moderately tolérant and Vigna unguiculata, tolerant. This classification agrees well with that of drought resistance of these species when grown in the field.
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