Heterologous expression of a lycophyte protein enhances angiosperm seedling vigor

AbstractSeedling vigor is a key agronomic trait that determines juvenile plant performance. Angiosperm seeds develop inside fruits and are connected to the mother plant through vascular tissues. Their formation requires plant-specific genes, such as BREVIS RADIX (BRX) in Arabidopsis thaliana roots. BRX family proteins are found throughout the angiosperms but also occur in non-vascular bryophytes and non-seed lycophytes. They consist of four conserved domains, including the tandem “BRX-domains”. We found that bryophyte or lycophyte BRX homologs can only partially substitute for Arabidopsis BRX (AtBRX) because they miss key features in the linker between the BRX-domains. Intriguingly however, expression of a BRX homolog from the lycophyte Selaginella moellendorffii (SmBRX) in A. thaliana wildtype background confers robustly enhanced root growth vigor that persists throughout the life cycle. This effect can be traced back to a substantial increase in seed and embryo size, and can be reproduced with a modified, “SmBRX-like” variant of AtBRX. Our results thus suggest that BRX variants could serve as biotechnological tools to boost seedling vigor and shed light on the activity of ancient, non-angiosperm BRX family proteins.</jats:p

Moves in the territory of literacy? - the telephone discourse of three- and four-year-olds.

The concept of the ‘new communication landscape’ (Kress, 1998) is propelling a re-examination of what is meant by literacy, and the ways in which we seek to identify and promote literacy practices in young children.This article reviews theoretical moves to destabilize the dichotomy between oracy and literacy. Challenges posed by an examination of new technologies are set against those that draw on evidence from diverse cultural and historical contexts.The telephone presents a contemporary context that has been largely overlooked in child language research – yet this medium possesses its own specific constraints and opportunities for discourse, necessitating a shift away from the ‘here-and-now’ characteristic of very young children’s talk, to a consideration of the interlocutor’s distance characteristic of literacy. An analysis of the practices of three- and four-year-old children’s spontaneous telephone play demonstrates many ways in which their oral practices in this communication channel may be conceptualiz21ed within an understanding of their symbolic meaningmaking practices that is related to literacy, rather than a separate domain of activity. Finally, it is proposed that Bakhtin’s notion of ‘speech genre’ provides a particularly useful characterization of this important aspect of language development in the context of communication technology