Red Mexican grapefruit: a novel source for bioactive limonoids and their antioxidant activity

Citrus limonoids have shown to inhibit the growth of cancer in colon, lung, mouth, stomach and breast in animal and cell culture studies. For the first time in the present study, an attempt has been made to isolate antioxidant fractions and five limonoids from red Mexican grapefruit seeds. Defatted seed powder was successively extracted with hexane, ethyl acetate (EtOAc), acetone, methanol (MeOH) and MeOH/water and the extracts were concentrated under vacuum. Radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and total phenolic content were also measured for comparison with the antioxidant capacity in the phosphomolybdenum method for the above extracts. Acetone and MeOH extracts, respectively, showed the highest (85.7%) and lowest (53.3%) radical scavenging activity, at 500 ppm. The total phenolic contents were found to be highest in the acetone extract (15.94%) followed by the MeOH extract (5.92%), ethyl acetate extract (5.54%) and water extract (5.26%). Antioxidant capacity of the extracts as equivalents to ascorbic acid (micromol/g of the extract) was in the order, EtOAc extract > acetone extract > water extract > methanol extract. Furthermore, the EtOAC and acetone extracts were loaded onto silica gel columns to obtain four limonoid aglycons. MeOH fraction was loaded onto a dowex-50 and sepabeads resin column to obtain a limonoid glucoside. The purity of the isolated five compounds was analyzed by HPLC using a C18 column and UV detection at 210 nm. Finally, the structures of the compounds were identified as obacunone, nomilin, limonin, deacetylnomilin (DAN) and limonin-17-beta-D-glucopyranoside (LG) using 1H and 13C NMR studies.     

Metalloids in plants: A systematic discussion beyond description

Metalloids represent a wide range of elements with intermediate physiochemical properties between metals and non-metals. Many of the metalloids, like boron, selenium, and silicon are known to be essential or quasi-essential for plant growth. In contrast, metalloids viz. arsenic and germanium are toxic to plant growth. The toxicity of metalloids largely depends on their concentration within the living cells. Some elements, at low concentration, may be beneficial for plant growth and development; however, when present at high concentration, they often exert negative effects. In this regard, understanding the molecular mechanisms involved in the uptake of metalloids by roots, their subsequent transport to different tissues and inter/intra-cellular redistribution has great importance. The mechanisms of metalloids' uptake have been well studied in plants. Also, various transporters, as well as membrane channels involved in these processes, have been identified. In this review, we have discussed in detail the aspects concerning the positive/negative effects of different metalloids on plants. We have also provided a thorough account of the uptake, transport, and accumulation, along with the molecular mechanisms underlying the response of plants to these metalloids. Additionally, we have brought up the previous theories and debates about the role and effects of metalloids in plants with insightful discussions based on the current knowledge.     

Identification of QTLs for Yield and Associated Traits in F₂ Population of Rice

Identification of quantitative trait loci (QTLs) controlling yield and yield-related traits in rice was performed in the F₂ mapping population derived from parental rice genotypes DHMAS and K343. A total of 30 QTLs governing nine different traits were identified using the composite interval mapping (CIM) method. Four QTLs were mapped for number of tillers per plant on chromosomes 1 (2 QTLs), 2 and 3; three QTLs for panicle number per plant on chromosomes 1 (2 QTLs) and 3; four QTLs for plant height on chromosomes 2, 4, 5 and 6; one QTL for spikelet density on chromosome 5; four QTLs for spikelet fertility percentage (SFP) on chromosomes 2, 3 and 5 (2 QTLs); two QTLs for grain length on chromosomes 1 and 8; three QTLs for grain width on chromosomes1, 3 and 8; three QTLs for 1000-grain weight (TGW) on chromosomes 1, 4 and 8 and six QTLs for yield per plant (YPP) on chromosomes 2 (3 QTLs), 4, 6 and 8. Most of the QTLs were detected on chromosome 2, so further studies on chromosome 2 could help unlock some new chapters of QTL for this cross of rice variety. Identified QTLs elucidating high phenotypic variance can be used for marker-assisted selection (MAS) breeding. Further, the exploitation of information regarding molecular markers tightly linked to QTLs governing these traits will facilitate future crop improvement strategies in rice.     

Niche shift in invasive species: is it a case of “home away from home” or finding a “new home”?

In recent years, there has been a rather acrimonious debate on matters concerning the biology of invasive species, some as fundamental as the definition and what constitutes an invasive species. However, an abiding commonality of all invasive species is the fact that they have all moved away from their native ranges to newer and often non-native ranges. In plants, Lantana camara has shifted from its native South American range distribution to most other parts of the world. In animals, the African giant snail has dispersed from Africa to most parts of Asia. What do such niche shifts signify about the nature and quality of the habitats to which the invasive species have moved? In this paper, using the classical niche paradigm, we analyse if niche shifts of thirty-three of the world’s top invasive species constitute just moving from one habitat to another similar habitat somewhere on the earth (home away from home) or that they have moved to totally new habitats (different from their native home). Surprisingly, our results show that for 90% of the world’s top invasive species, movements have been largely restricted to homes away from home, rather than into alien homes. This clearly indicates the potential inertia that species might face in moving out of their fundamental niche. We discuss these results in the context of the overall debate on invasion biology and how niche conservatism may have played a role in dampening the rates of invasion.

     

Taxonomic importance of seed macro‐ and micro‐morphology in Abelmoschus (Malvaceae)

Seed morphology of Abelmoschus is known to be variable, but patterns of variation have never been critically studied. We studied seed macro‐ and micro‐morphological characters, including seed shape/size, seed coat pattern and trichome density/structure in multiple samples to evaluate the taxonomic significance of seed characters. Among the studied characters, seed shape and trichome structure were found to have major taxonomic importance and proved to be valuable characters for separating taxa. Two main seed types were present: seeds with deciduous trichomes and seeds with persistent trichomes. These characters offer significant evidence to the distinctness of certain species (A. esculentus, A. moschatus subsp. moschatus, A. moschatus subsp. tuberosus, A. crinitus and A. angulosus). Further, our results indicate that A. moschatus subsp. tuberosus should be maintained as a separate subspecies while A. manihot subsp. tetraphyllus var. pungens may be merged in A. angulosus. No significant intraspecific variation was observed, except in A. esculentus. We conclude that seed coat sculpturing and seed trichomes do indeed provide stable and diagnostic characters for many morphologically closely related taxa of Abelmoschus and that LM/SEM techniques can be useful in solving systematic problems and management of Abelmoschus genetic resources.     

Allostery mediates ligand binding to WWOX tumor suppressor via a conformational switch

While being devoid of the ability to recognize ligands itself, the WW2 domain is believed to aid ligand binding to the WW1 domain in the context of a WW1–WW2 tandem module of WW domain‐containing oxidoreductase (WWOX) tumor suppressor. In an effort to test the generality of this hypothesis, we have undertaken here a detailed biophysical analysis of the binding of WW domains of WWOX alone and in the context of the WW1–WW2 tandem module to an array of putative proline‐proline‐x–tyrosine (PPXY) ligands. Our data show that while the WW1 domain of WWOX binds to all ligands in a physiologically relevant manner, the WW2 domain does not. Moreover, ligand binding to the WW1 domain in the context of the WW1–WW2 tandem module is two‐to‐three‐fold stronger than when treated alone. We also provide evidence that the WW domains within the WW1–WW2 tandem module physically associate so as to adopt a fixed spatial orientation relative to each other. Of particular note is the observation that the physical association of the WW2 domain with WW1 blocks access to ligands. Consequently, ligand binding to the WW1 domain not only results in the displacement of the WW2 lid but also disrupts the physical association of WW domains in the liganded conformation. Taken together, our study underscores a key role of allosteric communication in the ability of the WW2 orphan domain to chaperone physiological action of the WW1 domain within the context of the WW1–WW2 tandem module of WWOX. Copyright © 2015 John Wiley & Sons, Ltd.     

The Drosophila Hem/Kette/Nap1 protein regulates asymmetric division of neural precursor cells by regulating localization of Inscuteable and Numb

The Hem/Kette/Nap1 protein is involved in many biological processes. We have recently reported that Hem is required for the normal migration of neurons in the Drosophila embryo. In this paper, we report that Hem regulates the asymmetric division of neural precursor cells. We find that a well-studied Hem/Kette mutant allele produces at least two main, but possibly more, phenotypic classes of mutant embryos, and these phenotypes correlate with variable levels of maternal wild type Hem protein in the developing embryo. While the weaker class exhibits weak axon guidance defect and the mis-migration of neurons, the stronger class causes severe axon guidance defects, mis-migration of neurons and symmetric division of ganglion mother cells (GMC) of the RP2/sib lineage. We also show that the basis for the loss of asymmetric division is due to non-localization of Inscuteable and Numb in GMC-1. A non-asymmetric Numb segregates to both daughter cells of GMC-1, which then prevents Notch signaling from specifying a sib fate. This causes both cells to adopt an RP2 fate. Furthermore, loss of function for Abelson tyrosine kinase also causes loss of asymmetric localization of Inscuteable and Numb and symmetric division of GMC-1, the loss of function for WAVE has a very weakly penetrant loss of asymmetry defect. These results define another role for Hem/Kette/Nap1 in a neural precursor cell during neurogenesis.