फाइलोजेनेटिक्स और इवोल्यूशनरी बायोलॉजी जर्नल

Hox genes are highly conserved developmental genes involved in the patterning of the anterior-posterior axis of nearly all metazoan animals. While Hox genes have been characterized for many bilaterians, several cryptic taxa, often comprising microscopic specimens, have hitherto been neglected. We here present the first combined transcriptomic and genomic Hox gene study for Entoprocta (=Kamptozoa), a phylum of microscopic, sessile, tentacle-bearing animals with unresolved phylogenetic affinities. We identified 10 of the 11 Hox genes commonly found in other lophotrochozoans. The analyses of transcriptomic data of different developmental stages of three species (regenerating stages of the colonial species Pedicellina cernua, budding stages of the solitary species Loxosomella vivipara and embryos of the solitary species Loxosomella murmanica/atkinsae) yielded the Hox genes Labial, Hox3, Lox5, and Post2 in all species. Pb and Dfd were only found being expressed in the colonial species P. cernua. Lox4 was uniquely expressed in the solitary species L. vivipara and L. murmanica/atkinsae. Other homeobox genes belonging to the ANTP-class genes, e.g., ParaHox and NK-like genes, were also found. Thus, in addition to newly identified Hox genes (PceLox2-like & LviPost2-like), Entoporocta show the typical lophotrochozoan Hox pattern besides the loss of the posterior class Hox gene Post1.

Induction of colchitetraploidy was attempted in local Chrysanthemum carinatum (2n=18). The method used for colchicine treatment was “cotton swab method”. The details about the successful induction of polyploidy, morphological features and cytological (meiosis) are described and compared with control characters. The phenotypic characters observed such as slightly slower growth, stronger stem, thicker and larger leaves, lager flowers and seeds in the colchitetraploid plant. Cytological characters also such as increase cell size, chiasma frequency, DNA contents and double chromosome number in colchitetraploid plant compared with control. The growth pattern, morphology, pollen stain-ability and seed set were recorded; however, main emphasis was given on chromosomes behavior of control and isolated colchitetraploidy.

Evolvability has become a concept used to explain the common observation of clade asymmetry. However, the concept of evolvability means different things to different workers. Recent work has formalized the concept and we apply the formalized concept to a developmental system (primordial germ cell determination mechanism) that has been proposed to explain clade size disparity. In a simplified view, there are two general primordial germ cell (pgc) determination mechanisms: determinative and induced. The determinative mechanism is associated with species rich clades and the induced mechanism with species poor clades. The formal equations of evolvability provide a theoretical framework under which we can assess the relative influence of pgc determination mechanisms on clade evolvability. We propose that the determinative mechanism has enhanced evolvability in most clades that possess the trait.