Plant development

The PLETHORA genes mediate patterning of the Arabidopsis root stem cell niche. Aida, M. et al. Cell 119, 109–120 (2004)

In Arabidopsis thaliana, root stem-cells are maintained by a small set of organizing cells, known as the quiescent centre (QC), the location of which depends on auxin accumulation. By using a promoter-trap screen, the authors identified two putative transcription factors, PLETHORA 1 (PLT1) and PLT2, which are required for QC specification and for maintaining root stem-cells during embryonic pattern formation; in addition, evidence indicates that their expression in the QC responds to auxin.

Developmental biology

Foxa2 is required for transition to air breathing at birth. Wan, H. et al. Proc. Natl Acad. Sci. USA 101, 14449–14454 (2004)

A fundamental adaptation faced by a newborn mammal is the ability to breathe in air through its lungs. Now, by knocking out gene function in the epithelial cells of the developing mouse lung, Wan and colleagues show that Foxa2, which encodes a forkhead transcription factor, is a master gene required for lung maturation at birth. This finding could inform treatments for premature babies and for individuals with lung disease or injury.

Developmental biology

Hmx2 and Hmx3 homeobox genes direct development of the murine inner ear and hypothalamus and can be functionally replaced by Drosophila Hmx. Wang, W. et al. Dev. Cell 7, 439–453 (2004)

The authors show that the roles of mouse homeobox genes Hmx2 and Hmx3 in the development of the vestibular system are overlapping and distinct, but that their roles in the central nervous system (CNS) are interchangeable. Moreover, the single fly Hmx can rescue the CNS and inner-ear phenotype in double-knockout mice, despite differences in morphology. The authors propose that evolution of complex organs such as the vertebrate inner ear might involve cooption of primitive genetic programmes to new locations, not just from acquisition and modification of protein domains.

Gene expression

Genome-wide mRNA surveillance is coupled to mRNA export. Hieronymus, H. et al. Genes Dev., 1 November 2004 (doi: 10.1101/gad.1241204)

The authors found evidence to suggest that there are links between DNA and RNA surveillance and mRNA export. A screen of annotated, non-essential Saccharomyces cerevisiae genes identified new factors required for mRNA export, including Rrp6, an mRNA surveillance factor, and Lrp1, a DNA-repair protein. The authors found that Lrp1 can mediate mRNA degradation and requires Rrp6 for nuclear localization to the genes that encode their target mRNAs.