Functional analyses of genetic pathways controlling petal specification in poppy

MADS-box genes are crucial regulators of floral development, yet how their functions have evolved to control different aspects of floral patterning is unclear. To understand the extent to which MADS-box gene functions are conserved or have diversified in different angiosperm lineages, we have exploited the capability for functional analyses in a new model system, Papaver somniferum (opium poppy). P. somniferum is a member of the order Ranunculales, and so represents a clade that is evolutionarily distant from those containing traditional model systems such as Arabidopsis, Petunia, maize or rice. We have identified and characterized the roles of several candidate MADS-box genes in petal specification in poppy. In Arabidopsis, the APETALA3 (AP3) MADS-box gene is required for both petal and stamen identity specification. By contrast, we show that the AP3 lineage has undergone gene duplication and subfunctionalization in poppy, with one gene copy required for petal development and the other responsible for stamen development. These differences in gene function are due to differences both in expression patterns and co-factor interactions. Furthermore, the genetic hierarchy controlling petal development in poppy has diverged as compared with that of Arabidopsis. As these are the first functional analyses of AP3 genes in this evolutionarily divergent clade, our results provide new information on the similarities and differences in petal developmental programs across angiosperms. Based on these observations, we discuss a model for how the petal developmental program has evolved.     

Population continuity vs. discontinuity revisited: dental affinities among late Paleolithic through Christian-era Nubians

The present study revisits a subject that has been a source of long-standing bioarchaeological contention, namely, estimation of Nubian population origins and affinities. Using the Arizona State University dental anthropology system, frequencies of 36 crown, root, and intraoral osseous discrete traits in 12 late Pleistocene through early historic Nubian samples were recorded and analyzed. Specifically, intersample phenetic affinities, and an indication of which traits are most important in driving this variation, were determined through the application of correspondence analysis and the mean measure of divergence distance statistic. The results support previous work by the author and others indicating that population discontinuity, in the form of replacement or significant gene flow into an existing gene pool, occurred sometime after the Pleistocene. This analysis now suggests that the break occurred before the Final Neolithic. Samples from the latter through Christian periods exhibit relative homogeneity, which implies overall post-Pleistocene diachronic and regional population continuity. Yet there are several perceptible trends among these latter samples that: 1) are consistent with documented Nubian population history, 2) enable the testing of several existing peopling hypotheses, and 3) allow the formulation of new hypotheses, including a suggestion of two post-Pleistocene subgroups predicated on an age-based sample dichotomy.     

Endocrine events during pre-diapause and non-diapause larval-pupal development of the tobacco hornworm, Manduca sexta

The haemolymph ecdysteroid titre and in vitro capacities of prothoracic glands and corpora allata to synthesize ecdysone and juvenile hormone, respectively, during the last-larval instar of diapause-destined (short-day) and non-diapause-destined (long-day) Manduca sexta were investigated. In general, the ecdysteroid titres for both populations of larvae were the same and exhibited the two peaks characteristic of the haemolymph titre during this developmental stage in Manduca. The only difference in the titre occurred between day 7 plus 12 h and day 7 plus 20 h, when the short-day larval titre did not decrease as quickly as the long-day titre. The in vitro synthesis of ecdysone by prothoracic glands of short- and long-day larvae during the pharate pupal phase of the instar were also essentially the same. Activity fluctuated at times which would support the idea that ecdysone synthesis by the glands is a major contributing factor to the changes in the haemolymph ecdysteroid titre. There was one subtle difference in prothoracic gland activity between the two populations, occurring on day 7 plus 2 h. By day 7 plus 10 h, however, rates of ecdysone synthesis by the short- and long-day glands were comparable. This elevated activity of the short-day glands occurred just prior to the period the haemolymph ecdysteroid titre remained elevated in these larvae. The capacities of corpora allata to synthesize juvenile hormone I and III in vitro were not markedly different in long- and short-day last-instar larvae. At the time of prothoracicotropic hormone release in the early pupa, activity of corpora allata from short- and long-day reared animals was low and also essentially the same. There were a few differences in the levels of synthesis at isolated times, but they were not consistent for both homologues. Overall, there are no compelling differences in the fluctuations of ecdysteroids and juvenile hormones between diapause-destined and non-diapause-destined Manduca larvae. Since these hormones do not appear to play any obviously significant role in the induction of pupal diapause in this insect, the photoperiodic induction of diapause in Manduca appears to be a predominantly brain-centred phenomenon not involving endocrine effectors.     

Brief communication: First evidence of LSAMAT in non-native Americans: Historic Senegalese from West Africa

To date, the distinctive dental wear pattern known as LSAMAT, or “lingual surface attrition of the maxillary anterior teeth,” has been documented in prehistoric samples from Brazil, Panama, and Puerto Rico only. However, new data from a historic Senegalese sample reveals the first example of this wear pattern outside the Americas. The Senegal LSAMAT is present in 45% of 22 adult crania, and is associated with a caries rate of 40% in 38 adults (6.7% of 534 permanent teeth). A correlation between LSAMAT and caries was also observed in the Latin American samples. In these cases, it was hypothesized that LSAMAT was caused by the specialized consumption of an abrasive, high carbohydrate food, such as manioc. Manioc is a common cultigen in Senegal; thus, it may have also caused the African LSAMAT. The chewing of sugar cane could have been an additional, contributing factor. Am J Phys Anthropol 102:141–146, 1997. © 1997 Wiley-Liss, Inc.     

Development of maize plants from cultured shoot apices

Excised shoot apices of maize (Zea mays L.), comprising the apical meristem and one or two leaf primordia, have been cultured and can form rooted plantlets. The plantlets, derived from meristems that had previously formed 7–10 nodes, develop into mature, morphologically normal plants with as many nodes as seed-grown plants. These culture-derived plants exhibited the normal pattern of development, with regard to the progression of leaf lengths along the plant and position of axillary buds and aar shoots. Isolation of the meristem from previously formed nodes reinitiates the pattern and number of nodes formed in the new plant. Thus, cells of the meristem of a maize plant at the seedling stage are not determined to form a limited number of nodes.