Genetic-evolutionary studies on cultivated cannas

Summary Hybridization has played a dominant and decisive role in the origin of ornamental cannas. This has been made possible by the ecospecific differentiation of the parental species, which implies lack of barriers and a good deal of recombination associated with reasonably high fertility.Colour differences between species are controlled by a number of genes and their intensifiers, inhibitors, lethals, etc. From recombination in interspecific hybrids of such a wide range of genes, segregating simultaneously and involving complex segregation, arises a wide array of heterozygous genotypes with new colours and colour combinations, releasing much genetic diversity.Hybridization has also been responsible for transgressive segregation, particularly in length and breadth of staminodia and luxuriance, affecting not only plant height but also flower size. Perhaps the most important single factor responsible for the evolution of ornamental cannas has been the repeated cycles of hybridization which have led to the breakage of size and other barriers; this seems to have been exploited continuously until very large flower size was built up and combined with other useful vegetative and floral characters such as colour and number of flowers per inflorescence, extended blooming period, cold resistance, etc. The efficient vegetative propagation made fixing of the useful genotypes no problem, although they may contain a high degree of heterozygosity and sexual sterility.Along these lines, Année (hybrids between C. indica and C. glauca) and Ehemann (hybrids between C. iridiflora and C. warscwiczii) cannas came into being in 1848 and 1863 respectively. Although both were a distinct improvement over the original species, they were still relatively small-flowered and major improvements came roundabout 1868, when Crozy, Gladiolus or French Dwarf cannas (C. X generalis Bailey) were released. This group arose from hybrids and back crosses of the first two groups and contains diploids, interchange heterozygotes and autotriploids. When further intercrossing, inbreeding and selection yielded no significant improvement, new blood in the form of C. flaccida was introduced. The result was the release of Italian, Iris, Orchid or Giant flowered cannas (C. X orchiodes Bailey) in 1872. These are asynaptic seedless diploids and allo- or segmental allotriploids. By and large, Crozy cannas are the result of exploiting new genetic diversity and transgression, while Italian cannas owe their excellence to the luxuriance accompanying the introduction of C. flaccida.Next to hybridization, triploidy (14%) has been an important mechanism in the origin of cultivars with thicker, more durable and larger flower parts. The two types of triploids, autotriploids and segmental allotriploids, are distinguishable by their morphological and cytogenetical properties.It is evident that during the 44 years 1848–1892 the speed of evolution was rapid and its direction governed by the following principles of selection: increase in hardiness, reduction in height, spikes well above foliage, free flowering, erect flowers, increase in flower size, colour diversity, circular form of flowers, increase in thickness of flower parts and durability of flower, self shedding flowers, etc. The result has been the transformation of cannas from simple foliage plants to attractive ornamental flowers.It is noteworthy that selection for the two principal uses of canna not only involved different organs, but also took place in very different environments. While selection in ornamental canna was for floral parts under a temperate European climate new to Canna, that for starch involved the rhizome in its native habitat. It is interesting that the two different purposes of selection under different habitats have both ended in triploidy: in the ornamentals this has considerably enlarged the flowers, while in the starch-yielding C. edulis it has enlarged the fleshy rhizome but had a very limited effect on the flower.     

A COMPARATIVE STUDY OF THE ULTRASTRUCTURE OF MICROVILLI IN THE EPITHELIUM OF SMALL AND LARGE INTESTINE OF MICE

A comparative analysis of the fine structure of the microvilli on jejunal and colonic epithelial cells of the mouse intestine has been made. The microvilli in these two locations demonstrate a remarkably similar fine structure with respect to the thickness of the plasma membrane, the extent of the filament-free zone, and the characteristics of the microfilaments situated within the microvillous core. Some of the core microfilaments appear to continue across the plasma membrane limiting the tip of the microvillus. The main difference between the microvilli of small intestine and colon is in the extent and organization of the surface coat. In the small intestine, in addition to the commonly observed thin surface "fuzz," occasional areas of the jejunal villus show a more conspicuous surface coat covering the tips of the microvilli. Evidence has been put forward which indicates that the surface coat is an integral part of the epithelial cells. In contrast to the jejunal epithelium, the colonic epithelium is endowed with a thicker surface coat. Variations in the organization of the surface coat at different levels of the colonic crypts have also been noted. The functional significance of these variations in the surface coat is discussed.     

Infradian rhythmicity in egg production features in relation to antioxidant profiles of Rhode Island Red (RIR) birds reared at backyard in different agroclimatic zones of West Bengal during summer stress

Egg production features viz. weekly hen day and egg weight together with some stress markers were studied in RIR birds reared under backyard in different agroclimatic zones of West Bengal. Overall, weekly hen day average and egg weight in summer was 3.39 ± 0.09 and 45.13 ± 0.24 g, respectively. But the pattern of egg production in various zones is not same, as significant egg production difference (P ≤ 0.01) among zones was noticed in summer, from 26th to 37th week. There was significant (P ≤ 0.01) correlation between weekly hen day average and egg weight on 26th, 35th and 37th week (P ≤ 0.05). The observed overall level of antioxidant enzymes viz. SOD (U/g of Hb), glutathione peroxidase (GSH-Px) (μmol/L), TAS (mmol/L) and LDH (IU/L) were 0.56 ± 0.61, 565.15 ± 0.61, 1.43 ± 0.61 and 203.05 ± 0.61, respectively, irrespective of zones. It was observed that mean concentration of SOD, GHS-Px, TAS and LDH of RIR birds reared at backyard have positive association with weekly hen day average and average egg weight throughout summer stress. The current findings showed that RIR birds reared at backyard had better adaptation ability to summer stress in different agroclimatic zones of West Bengal.     

Cyclic mismatch binding ligand CMBL4 binds to the 5′-T-3′/5′-GG-3′ site by inducing the flipping out of thymine base

A newly designed cyclic bis-naphthyridine carbamate dimer CMBL4 with a limited conformational flexibility was synthesized and characterized. Absorption spectra revealed that two naphthyridines in CMBL4 were stacked on each other in aqueous solutions. The most efficient binding of CMBL4 to DNA was observed for the sequence 5′-T-3′/5′-GG-3′ (T/GG) with the formation of a 1:1 complex, which is one of possible structural elements involved in the higher order structures of (TGG)_n repeat DNA triggering the genome microdeletion. Surface plasmon resonance assay also showed the binding of CMBL4 with TGG repeat DNA. Potassium permanganate oxidation studies of CMBL4-bound duplex containing the T/GG site showed that the CMBL4-binding accelerated the oxidation of thymine at that site, which suggests the flipping out of the thymine base from a π-stack. Preferential binding was observed for CMBL4 compared with its acyclic variants, which suggests the marked significance of the macrocyclic structure for the recognition of the T/GG site.     

Influence of Microbial Composition on the Carbon Storage Capacity of the Mangrove Soil at the Land-ocean Boundary in the Sundarban Mangrove Ecosystem,India

Spatiotemporal assessment of the mangrove soil of Indian Sundarban revealed that decomposition rate of the organic matter was significantly lower in the anoxic condition than that of the oxic condition. Higher degree of enzyme activity in the oxic soil than the anoxic condition suggested that slower biomineralization in anoxic condition would facilitate long-term storage of organic matter in that particular ecosystem. Microbial population of nitrifying bacteria, phosphate solubilizing bacteria, cellulose degrading bacteria and fungi showed significant reduction in anoxic incubation than that in oxic incubation. In contrary, sulfate reducing bacteria and free living N2 fixing bacteria showed higher population in anoxic incubation indicating their preference for anaerobic condition. Soil CO₂ emission rate decreased with the increase in anoxicity and was largely dependent on the soil redox potential, organic carbon and microbial population of the mangrove soil.     

Split-ubiquitin yeast two-hybrid interaction reveals a novel interaction between a natural resistance associated macrophage protein and a membrane bound thioredoxin in Brassica juncea

Natural resistance associated macrophage proteins (NRAMPs) are evolutionarily conserved metal transporters involved in the transport of essential and nonessential metals in plants. Fifty protein interactors of a Brassica juncea NRAMP protein was identified by a Split-Ubiquitin Yeast-Two-Hybrid screen. The interactors were predicted to function as components of stress response, signaling, development, RNA binding and processing. BjNRAMP4.1 interactors were particularly enriched in proteins taking part in photosynthetic or light regulated processes, or proteins predicted to be localized in plastid/chloroplast. Further, many interactors also had a suggested role in cellular redox regulation. Among these, the interaction of a photosynthesis-related thioredoxin, homologous to Arabidopsis HCF164 (High-chlorophyll fluorescence164) was studied in detail. Homology modeling of BjNRAMP4.1 suggested that it could be redox regulated by BjHCF164. In yeast, the interaction between the two proteins was found to increase in response to metal deficiency; Mn excess and exogenous thiol. Excess Mn also increased the interaction in planta and led to greater accumulation of the complex at the root apoplast. Network analysis of Arabidopsis homologs of BjNRAMP4.1 interactors showed enrichment of many protein components, central to chloroplastic/cellular ROS signaling. BjNRAMP4.1 interacted with BjHCF164 at the root membrane and also in the chloroplast in accordance with its proposed function related to photosynthesis, indicating that this interaction occurred at different sub-cellular locations depending on the tissue. This may serve as a link between metal homeostasis and chloroplastic/cellular ROS through protein–protein interaction.     

The role of introns in the conservation of the metabolic genes of Arabidopsis thaliana

In Arabidopsis thaliana, primary metabolic genes (PMGs) are more evolutionarily conserved and intron-rich than secondary metabolic genes. We observed that PMGs are more primitive and pan-taxonomically persistent as compared to secondary (SMGs) and non-metabolic genes (NMGs). This difference in primitiveness and persistence is primarily correlated with intron number and is independent of gene expression level. We propose a twofold explanation behind higher intron enrichment in PMGs. Firstly, introns might increase protein versatility amongst PMGs through alternative splicing, providing selective advantage of PMGs and making them more persistent across diverse plant taxa. Also, multifunctional PMGs may acquire functional domains by increasing the intronic burden. Additionally, single nucleotide polymorphisms (SNPs) accumulate at a higher rate in introns as compared to exons. Moreover, a strong negative correlation between cumulative exonic SNPs density and intron number indicates that introns may protect the exonic regions against the deleterious effect of these mutations, making them more conserved.