We report an improved draft nucleotide sequence of the 2.3-gigabase genome of maize, an important crop plant and model for biological research. Over 32,000 genes were predicted, of which 99.8% were placed on reference chromosomes. Nearly 85% of the genome is composed of hundreds of families of transposable elements, dispersed nonuniformly across the genome. These were responsible for the capture and amplification of numerous gene fragments and affect the composition, sizes, and positions of centromeres. We also report on the correlation of methylation-poor regions with Mu transposon insertions and recombination, and copy number variants with insertions and/or deletions, as well as how uneven gene losses between duplicated regions were involved in returning an ancient allotetraploid to a genetically diploid state. These analyses inform and set the stage for further investigations to improve our understanding of the domestication and agricultural improvements of maize.

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The peptides vasopressin (VP) and oxytocin are derived from preprohormone precursers encoded by highly homologous linked genes that are expressed in discrete groups of hypothalamic neurons. The mature hormones are released into the peripheral circulation from the neural (posterior) lobe of the pituitary and have also been implicated in the regulation of anterior lobe. We have used Northern blotting and in situ hybridization to RNA in tissue sections to describe the presence, anatomical localization, and regulation of VP and oxytocin RNAs in the pituitary gland itself. We were unable to detect VP transcripts in the anterior and intermediate lobes of the pituitary. Rather we found low levels of VP RNA in the neural lobe. Furthermore, the osmotic stimulation of a 2%

In rats, a shift from somatotroph dominance to lactotroph dominance during pregnancy and lactation is well reported. Somatotroph to lactotroph transdifferentiation and increased lactotroph mitotic activity are believed to account for this and associated pituitary hypertrophy. A combination of cell death and transdifferentiation away from the lactotroph phenotype has been reported to restore non-pregnant pituitary proportions after weaning. To attempt to confirm that a similar process occurs in mice, we generated and used a transgenic reporter mouse model (prolactin (PRL)-Cre/ROSA26-expression of yellow fluorescent protein (EYFP)) in which PRL promoter activity at any time resulted in permanent, stable, and highly specific EYFP. Triple immunochemistry for GH, PRL, and EYFP was used to quantify EYFP+ve, PRL−ve, and GH+ve cell populations during pregnancy and lactation, and for up to 3 weeks after weaning, and concurrent changes in cell size were estimated. At all stages, the EYFP reporter was expressed in 80% of the lactotrophs, but in fewer than 1% of other pituitary cell types, indicating that transdifferentiation from those lactotrophs where reporter expression was activated is extremely rare. Contrary to expectations, no increase in the lactotroph/somatotroph ratio was seen during pregnancy and lactation, whether assessed by immunochemistry for the reporter or PRL: findings confirmed by PRL immunochemistry in non-transgenic mice. Mammosomatotrophs were rarely encountered at the age group studied. Individual EYFP+ve cell volumes increased significantly by mid-lactation compared with virgin animals. This, in combination with a modest and non-cell type-specific estrogen-induced increase in mitotic activity, could account for pregnancy-induced changes in overall pituitary size.

We investigated the effects of thyroid status on nitric oxide synthase (NOS) gene expression in the rat hypothalamic paraventricular (PVN) and supraoptic nuclei (SON). Propylthiouracil (PTU)-induced hypothyroidism in male rats produced a highly significant reduction in NOS gene transcripts in the PVN and SON, as assessed by quantitative in situ hybridization histochemistry with a specific oligodeoxynucleotide probe. The addition of T3 (40 micrograms/kg) to the PTU-containing diet completely prevented the reduction in NOS transcripts. Hyperthyroidism, induced by adding 160 micrograms/kg T3 to the food, more than doubled the prevalence of NOS transcripts in the PVN and SON after a similar time. Up-regulation of NOS gene transcripts induced by the osmotic stimulus of chronic salt loading was markedly attenuated by PTU-induced hypothyroidism. These results demonstrate a major effect of thyroid status on regulation of NOS gene expression in the hypothalamus.