Arginine decarboxylase (polyamine synthesis) mutants of Arabidopsis thaliana exhibit altered root growth

Putrescine and polyamines are produced by two alternative pathways in plants. One pathway starts with the enzyme arginine decarboxylase; the other with ornithine decarboxylase. The authors developed an in vivo screening strategy to identify mutants with low levels of arginine decarboxylase activity. The screen requires both a primary screen of the M2 generation and a secondary screen of the M3 generation. The method used was to screen 15 000 EMS-mutagenized M2 seedlings for low levels of arginine decarboxylase (ADC) activity and identified seven mutants that fall into two complementation groups. These mutants have from 20% to 50% of wild-type enzyme activity. Morphological alterations common among the mutants include increased levels of lateral root branching. The authors obtained a double mutant combining the alleles with the lowest activities from the two complementation groups; this has lower ADC enzyme activity and putrescine levels than either of the single mutants. The double mutant has highly kinked roots that form a tight cluster; it also has narrower leaves, sepals, and petals than either single mutant or wild-type, and delayed flowering. These results suggest there may be more than one ADC gene in Arabidopsis, and that ADC and polyamine levels play roles in root meristem function and in lateral growth of leaf-homolog organs.     

Status referents in long-tailed macaques (Macaca fascicularis): Precursors and effects of a female rebellion

The antecedents and consequences of a change in status in the female line have been documented in the course of an ongoing study of a captive colony ofMacaca fascicularis. A conjunction of two events appears to have been a cause of the timing. The first is the maturation of the eldest female offspring of the subordinate lineage, and the second the insertion of an intrauterine device into the mother of that lineage. These changes made these two females simultaneously sexual associates of the adult male, while the dominant female of the other lineage was still pregnant. In the course of these events the maturing sub-adult female of the subordinate lineage underwent the most dramatic change of status, eventually rising from the lowest position to that of alpha female. The complex changes which heralded this alternation in status are described in terms of the referent relations and alliances which were evolving in the group. The word “revolution” is reserved for a change in the type of social structure brough about by insurrection: rebellion occurs when insurrection changes the position of the individuals in a structure which is itself left unchanged -vide, Webster’s English Dictionary.