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J A Bryant

Publications and source records attributed to J A Bryant.

35 records · Page 2Linked to original sources
PubMed1985

Isolation of a fraction from cauliflower mosaic virus-infected protoplasts which is active in the synthesis of (+) and (-) strand viral DNA and reverse transcription of primed RNA templates.

Sub-cellular fractions, isolated from cauliflower mosaic virus (CaMV)-infected turnip protoplasts, are capable of synthesising CaMV DNA in vitro on an endogenous template and of reverse transcribing oligo dT-primed cowpea mosaic virus RNA. The activity was not detected in mock-inoculated protoplasts. In vitro-labelled DNA hybridized to single-stranded M13 clones complementary to the putative origins of (-) and (+) strand CaMV DNA synthesis and to restriction endonuclease fragments encompassing more than 90% of the CaMV genome. The synthesis of (-) and (+) strand DNA appeared asymmetric. The template(s) for in vitro CaMV DNA synthesis are in a partially nuclease-resistant form. Fractions capable of in vitro CaMV DNA synthesis contained CaMV RNA both heterogeneous and as discrete species; they also contained a range of different sizes of CaMV DNA. Several lines of evidence indicate that this range of in vitro-labelled CaMV DNA, extending from 0.6kb to 8.0kb in length, represents elongating (-) strand DNA. These are discussed in relation to their role as possible replicative intermediates.

Cloning, Molecular↗
PubMed1985

Effects of psoralen on replicon size and mean rate of DNA synthesis in partially synchronized cells of Pisum sativum L.

We have examined by fibre autoradiography the spacing of replicons in pea root meristems during synchronized entry into S phase from arrest at the G1/S boundary. Pretreatment with the DNA cross-linking agent, psoralen, produces a marked shortening of replicon spacing, suggesting that premature arrest of the replication fork results in the recruitment of additional initiation points within a given replicon family. This is discussed in relation to models for the control of DNA replication.

Autoradiography↗
PubMed1984

Phosphoenolpyruvate carboxylase from pennywort (Umbilicus rupestris). Changes in properties after exposure to water stress.

Umbilicus rupestris (pennywort) switches from C3 photosynthesis to an incomplete form of crassulacean acid metabolism (referred to as 'CAM-idling') when exposed to water stress (drought). This switch is accompanied by an increase in the activity of phosphoenolpyruvate carboxylase. This enzyme also shows several changes in properties, including a marked decrease in sensitivity to acid pH, a lower Km for phosphoenolpyruvate, very much decreased sensitivity to the allosteric inhibitor malate, and increased responsiveness to the allosteric effector glucose 6-phosphate. The Mr of the enzyme remains unchanged, at approx. 185 000. These changes in properties of phosphoenolpyruvate carboxylase are discussed in relation to the roles of the enzyme in C3 and in CAM plants.

Carboxy-Lyases↗
PubMed1983

Molecular weights of the major DNA polymerases in a higher plant, Pisum sativum L. (PEA).

The molecular weights of the soluble (alpha-like) and chromatin-bound (beta-like) DNA polymerases of pea have been determined. The bulk of the soluble activity consists of molecular species of ca 101,500 and ca 140,000 molecular weights. Smaller (49,000) and larger (182,000 and 234,000) species are also observed in some preparations. The chromatin-bound DNA polymerase exhibits a molecular weight of ca 50,000, although a larger (ca 88,000) species is also detected under conditions which favour aggregate formation.

Chromatin↗