Development of secondary inflorescences and in vitro plantlets from inflorescence cultures of Amaranthus paniculatus

Immature inflorescences of Amaranthus paniculatus were used as explants for in vitro culture studies. When placed on a medium supplemented with 3–6 mg/l kinetin, explants developed into secondary inflorescences. Leaves and shoots developed following culture of inflorescence tissue on media containing 8–15 mg/l kinetin or 5–10 mg/l BAP. These shoots when subcultured on MS medium supplemented with 12 mg/l kinetin + 15% coconut milk, formed roots. These rooted plantlets later flowered in vitro.Abbreviations MS Murashige and Skoog - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - BAP 6-benzylaminopurine - Kn 6-furfurylaminopurine - CM coconut milk     

Glyoxalase I from Brassica juncea is a calmodulin stimulated protein.

Brassica juncea glyoxalase I (S-lactoylglutathione-lyase, EC 4.4.1. 5) is a 56 kDa, heterodimeric protein. It requires magnesium (Mg2+) for its optimal activity. In this report we provide biochemical evidence for modulation of glyoxalase I activity by calcium/calmodulin (Ca2+/CaM). In the presence of Ca2+ glyoxalase I showed a significant (2.6-fold) increase in its activity. It also showed a Ca2+ dependent mobility shift on denaturing gels. Its Ca2+ binding was confirmed by Chelex-100 assay and gel overlays using 45CaCl2. Glyoxalase I was activated by over 7-fold in the presence of Ca2+ (25 microM) and CaM (145 nM) and this stimulation was blocked by the CaM antibodies and a CaM inhibitor, trifluroperazine (150 microM). Glyoxalase I binds to a CaM-Sepharose column and was eluted by EGTA. The eluted protein fractions also showed stimulation by CaM. The stimulation of glyoxalase I activity by CaM was maximum in the presence of Mg2+ and Ca2+; however, magnesium alone also showed glyoxalase I activation by CaM.     

Suppression of pea nuclear topoisomerase I enzyme activity by pea PCNA

Proliferating cell nuclear antigen (PCNA), a highly conserved DNA polymerase accessory protein of eukary- otic kingdom, has not been studied thoroughly in bio- chemical terms in plants. We describe the isolation of the cDNA encoding PCNA from the pea cDNA library using the PCR approach. The cDNA was used for expression of pea PCNA in bacteria as a fusion protein (GST.PCNA) with the GST tag at the amino terminal end. The GST.PCNA stimulated the partially purified pea DNA polymerases approximately 30-fold. The stimulation was due to the oligomeric form of GST.PCNA. The pea PCNA interacted with the recombinant type I pea topoiso- merase as well as the native pea nuclear topoisomerase I and repressed the DNA relaxation activities. However, the DNA binding activity of Topo I remained undisturbed in the presence of high amounts of PCNA, thereby signify- ing that the catalysis of Topo I was probably affected by PCNA.     

Phytochrome and Calcium Regulated Protein Phosphorylation in Sorghum bicolor

Irradiation with red light of Sorghum bicolor seedlings stimulated in vitro phosphorylation of 55 kD and several other soluble polypeptides in a development-dependent manner. The red light stimulated phosphorylation of 55 kD polypeptide was more in 6-day-old etiolated plants as compared to 5-day-old plants. The in vitro phosphorylation of 55 kD polypeptide was enhanced further when calcium was added to the extracts obtained from red light irradiated tissues of 6-day-old seedlings. This effect was inhibited in the presence of calmodulin inhibitors. There was no significant stimulation in the phosphorylation of this polypeptide by calcium in 5-day-old and 7-day-old etiolated plants. Besides 55 kD, the phosphorylation of several other polypeptides was either stimulated or inhibited by light, calcium and calmodulin inhibitors suggesting involvement of both kinases and phosphatases in light-mediated phosphorylation.     

Molecular systematics and paleobiogeography of the South American sigmodontine rodents [published erratum appears in Mol Biol Evol 1998 Feb;15(2):224]

The murid rodent subfamily Sigmodontinae contains 79 genera which are distributed throughout the New World. The time of arrival of the first sigmodontines in South America and the estimated divergence time(s) of the different lineages of South American sigmodontines have been controversial due to the lack of a good fossil record and the immense number of extant species. The "early-arrival hypothesis" states that the sigmodontines must have arrived in South America no later than the early Miocene, at least 20 MYA, in order to account for their vast present-day diversity, whereas the "late-arrival hypothesis" includes the sigmodontines as part of the Plio-Pleistocene Great American Interchange, which occurred approximately 3.5 MYA. The phylogenetic relationships among 33 of these genera were reconstructed using mitochondrial DNA (mtDNA) sequence data from the ND3, ND4L, arginine tRNA, and ND4 genes, which we show to be evolving at the same rate. A molecular clock was calibrated for these genes using published fossil dates, and the genetic distances were estimated from the DNA sequences in this study. The molecular clock was used to estimate the dates of the South American sigmodontine origin and the main sigmodontine radiation in order to evaluate the "early-" and "late-arrival" scenarios. We estimate the time of the sigmodontine invasion of South America as between approximately 5 and 9 MYA, supporting neither of the scenarios but suggesting two possible models in which the invading lineage was either (1) ancestral to the oryzomyines, akodonts, and phyllotines or (2) ancestral to the akodonts and phyllotines and accompanied by the oryzomyines. The sigmodontine invasion of South America provides an example of the advantage afforded to a lineage by the fortuitous invasion of a previously unexploited habitat, in this case an entire continent.      

The induction of allophanate lyase during the vegetative cell cycle in light-synchronized cultures of Chlamydomonas reinhardi.

Allophanate lyase can be induced by urea or acetamide 20-40-fold within 4 h in NH4 + -deprived cultures of Chlamydomonas reinhardi. In light-synchronized cultures, allophanate lyase induction appeared to be limited to the light phase of the cell cycle, provided that culture samples were induced under ongoing illumination conditions (i.e. light induction of light phase cells and dark induction of dark phase cells). However, when culture samples were induced under constant light conditions this cell cycle pattern was abolished. Light was found to be required for allophanate lyase induction and this was shown to be due, in part, to the light requirement for inducer uptake. The relationship between allophanate lyase induction and gametogenesis is discussed.     

Phytochrome regulation of peroxidase activity in maize IV. Photosynthetic independence of peroxidase enhancement

The continuous far-red light mediation of the enhancement ofperoxidase activity was repressed only partially by inhibitorsof cyclic and non-cyclic photophosphorylation. Under far-redlight the chlorophyll development was minimal and plastids weredifferentiated only partially. Isolated plastids from seedlingsgrown under far-red light developed photosystem I and II activityafter a lag of 4 hr, cyclic photophosphorylation after 8 hr,and non-cyclic photophosphorylation at 24 hr. These seedlings,however, failed to show CO²-dependent oxygen evolution upto24 hr of irradiation. The magnitudes of the various photochemicalactivities developed under far-red light were considerably lowerthan those developed under white light. Photosynthetic participationin the far-red mediated ‘high irradiance reaction’was excluded as it had a longer lag than the onset of the enhancementof peroxidase activity, and its magnitude was minimal. ¹Present address: School of Life Sciences, University of Hyderabad,Hyderabad-500001, India. (Received February 26, 1979; )