Effect of 2-benzoxazolinone (BOA) on seedling growth and associated biochemical changes in mung bean (Phaseolus aureus)

BOA (2-benzoxazolinone) is a potent phytotoxin present in several graminaceous crops such as rye, maize and wheat. Due to its wide range of phytotoxicity, it is considered as a potential pesticide. A study was conducted to explore the impact of BOA on the radicle and plumule elongation of mung bean (Phaseolus aureus) and associated changes in the macromolecular content - proteins and carbohydrates - and activities of enzymes like amylases, proteases, polyphenol oxidases and peroxidases. BOA significantly reduced the radicle and plumule length of P. aureus, and the contents of proteins and carbohydrates in both root and leaf tissue. On the other hand, activities of hydrolytic enzymes - proteases, amylases, polyphenol oxidases and peroxidases - increased substantially in both root and leaf tissue of P. aureus upon BOA exposure. This indicated that BOA treatment induced stress in P. aureus and enhanced enzyme activities to counter the induced stress and continue the growth. In other words, BOA-induced stress altered the plant biochemical status and related enzyme activities resulting in increased metabolism that serves to provide protection against cellular injury. Such studies providing information about the biomolecular content and enzymatic activities in response to natural products serve as clues for furtherance of knowledge about the modes of action of natural compounds of commercial interest.     

Growth correlations in shoot apices ofBrassica campestris L. during transition to flowering

Growth correlations in the shoot apical meristem during transition to flowering were studied in a quantitative long day plant,Brassica campestris L. cv. Ceres, requiring only one long day for floral initiation. During photo-inductive exposure of the plants, an overall increase in cell number could be observed at the shoot apex concomitant with promotion of leaf initiation. Release from apical dominance and decline in relative growth rate of leaf primordia are reported as early effects of photo-induction. With the onset of floral differentiation, production of new leaf primordia had stopped altogether. Maximum increase in RNA concentration could be noticed in axillary meristems following photoperiodic treatment, whereas in vegetative plants the highest RNA concentration was found in leaf primordia. The significance of these changes occurring during transition to flowering is discussed.     

Crop seed oil bodies: From challenges in protein identification to an emerging picture of the oil body proteome

Oleaginous seeds store lipids in specialized structures called oil bodies (OBs). These organelles consist of a core of neutral lipids bound by proteins embedded in a phospholipid monolayer. OB proteins are well conserved in plants and have long been grouped into only two categories: structural proteins or enzymes. Recent work, however, which identified other classes of proteins associated with OBs, clearly shows that this classification is obsolete. Proteomics‐mediated OB protein identification is facilitated in plants for which the genome is sequenced and annotated. However, it is not clear whether this knowledge can be dependably transposed to less well‐characterized plants, including the well‐established commercial sources of seed oil as well as the many others being proposed as novel sources for biodiesel, especially in Africa and Asia. Toward an update of the current data available on OB proteins this review discusses (i) the specific difficulties for proteomic studies of organelles; (ii) a 2012 census of the proteins found in seed OBs from various crops; (iii) the oleosin composition of OBs and their role in organelle stability; (iv) PTM of OB proteins as an emerging field of investigation; and finally we describe the emerging model of the OB proteome from oilseed crops.     

Rice Resistance to Planthoppers and Leafhoppers

For over 50 years, host-plant resistance has been regarded as an efficient method to reduce yield losses to rice caused by delphacid and cicadelid hoppers. Already a number of resistant rice varieties have been developed and deployed throughout Asia. To date, over 70 hopper resistance genes have been identified in rice; however, less than 10 genes have been deliberately introduced to commercial rice varieties. Currently, due to recent brown planthopper (Nilaparvata lugens [Stål]) and whitebacked planthopper (Sogatella furcifera [Horvath]) outbreaks occurring at an unprecedented scale, researchers are working toward a second generation of resistant varieties using newly identified gene loci and applying new molecular breeding methods. This paper reviews advances in the identification of resistance genes and QTLs against hoppers in rice. It collates all published information on resistance loci and QTLs against the major rice planthoppers and leafhoppers and presents information on gene locations, genetic markers, differential varieties, and wild rice species as sources of resistance. The review indicates that, whereas progress in the identification of genes has been rapid, considerable tidying of the information is required, especially regarding gene nomenclature and resistance spectra. Furthermore, sound information on gene functioning is almost completely lacking. However, hopper responses to resistance mechanisms are likely to be similar because a single phenotyping technique has been applied by most national and international breeding programs during germplasm screening. The review classifies genes occurring at two chromosome regions associated with several identified resistance loci and highlights these (Chr4S: BphR-R and Chr12L: BphR-R) as general stress response regions. The review calls for a greater diversity of phenotyping methods to enhance the durability of resistant varieties developed using marker-aided selection and emphasizes a need to anticipate the development of virulent hopper populations in response to the field deployment of genes.     

A specific DNA sequence is required for high frequency of recombination in the ade6 gene of fission yeast.

The point mutation M26 in the ade6 gene of Schizosaccharomyces pombe increases recombination frequency by an order of magnitude in comparison with other mutations in the same gene. The hypothesis is tested that this hot spot of recombination requires a specific nucleotide sequence at the M26 site. The DNA sequence is altered systematically by in vitro mutagenesis, and the resulting sequences are introduced into the ade6 gene in vivo by gene replacement. It results that any change of the heptanucleotide ATGACGT leads to loss of high frequency of recombination. Thus this oligonucleotide sequence is necessary for high frequency of recombination, but it seems not to be sufficient.     

Combined effect of 24-epibrassinolide and salicylic acid mitigates lead (Pb) toxicity by modulating various metabolites in <Emphasis Type="BoldItalic">Brassica juncea</Emphasis> L. seedlings

The present study demonstrated the combined effect of 24-epibrassinolide and salicylic acid against lead (Pb, 0.25, 0.50, and 0.75 mM) toxicity in Brassica juncea seedlings. Various parameters including water status, metal uptake, total water- and lipid-soluble antioxidants, metal chelator content (total thiols, protein-bound thiols, and non-protein-bound thiols), phenolic compounds (flavonoids, anthocyanins, and polyphenols), and organic acids were studied in 10-day-old seedlings. Dry matter content and the heavy metal tolerance index were reduced by 42.24 and 52.3%, respectively, in response to Pb treatment. Metal uptake, metal-chelating compounds, phenolic compounds, and organic acids were increased in Pb-treated seedlings as compared to control plants. The treatment of Pb-stressed seedlings with combination of EBL and SA resulted in enhancement of heavy metal tolerance index by 40.07%, water content by 1.84%, and relative water content by 23.45%. The total water- and lipid-soluble antioxidants were enhanced by 21.01 and 2.21%, respectively. In contrast, a significant decline in dry weight, metal uptake, thiol, and polyphenol contents was observed following the application of 24-epibrassinolide and salicylic acid. These observations indicate that Pb treatment has an adverse effect on B. juncea seedlings. However, co-application of 24-epibrassinolide and salicylic acid mitigates the negative effects of Pb, by lowering Pb metal uptake and enhancing the heavy metal tolerance index, water content, relative water content, antioxidative capacities, phenolic content, and organic acid levels.     

Growth regulatory response of parthenin and its derivatives

Parthenin and its pyrolysed and photo-derivatives exhibit a range of growth regulatory effects depending on their structure. At 5 mg L-1 (the lowest concentration used) the activity of all parthenin derivatives was greater than that of indole-3-acetic acid (IAA) in biotests based on growth and morphogenetic response of hypocotyl cuttings of Phaseolus aureus. Seedling growth was greatly enhanced by pyrolysed parthenin whereas parthenin and photo-parthenin promoted rooting of the hypocotyl cuttings. Structural changes in parthenin resulting from chemical and photochemical reactions, therefore, alter its growth regulatory action.     

Impedance of goat lens as a function of frequency at DC voltages 0, 50, 100, 200 mV

Impedance characteristics of lens tissue has been studied using the AC impedance system (EG&G PARC, model 318) at different low voltage excitations using a Cole-Cole Plot. The extracellular resistance (Re), intracellular resistance (Ri), depressed angle (theta), total impedance (/Z/), and phase angle (phi) of the tissue were measured. The impedance locus between the real part (Z') and imaginary part (Z') of the complex impedance of lens was examined at discrete frequencies ranging from 10 mHz to 10 Hz. A decrease in extra-cellular resistance (Re) and increase in distribution of the factor (alpha) of 56.8 KOmega, 48.1 KOmega, 32.8 KOmega, 13.4 KOmega, and 0.40, 0.43, 0.46, 0.53 were found at 0 mV, 50 mV, 100 mV, and 200 mV, respectively. The total impedance (/Z/) and phase angle (phi) were also evaluated and the observed frequency dependent for the frequency range was tested as a function of excitation voltage. An attempt has been made to explain the effect of voltage stress on lens impedance.