A life course approach to understanding social drivers of rangeland conversion

Grassland to woodland conversion, also known as woody plant encroachment (WPE), is a global-scale phenomena caused in large part by changes in social processes that affect rural land use patterns. Woody plant encroachment has raised serious concerns for species conservation, provision of ecosystem services, and viability of rural livelihoods and cultures. We examined the social drivers of WPE using a case study of rangelands in a semi-arid watershed. We employed the life course framework to understand how ranchers have made land ranch management decisions in the context of time, culture, and social change. We interviewed landowners whose families have been on the land for at least two generations to examine (1) the social context influencing a landowner's decision to increase or decrease their involvement in ranching over their life span, and (2) the historical events that facilitated constrained involvement. We relate these changes in involvement to the expansion of woody plants. Three major turning points were related to changes in ranching involvement: graduating high school, retirement, and infirmity of a parent. We found that changes in ranching involvement were influenced by large-scale shifts in culture, market regulations, and land values throughout the 20th century. These shifts led to three behavioral changes on the land that facilitated WPE: (1) changes in livestock following the collapse of the sheep and goat market, (2) increased popularity of hunting, and (3) decreased labor availability on the ranch. These observations illustrate the complex social and ecological forces at work throughout the 20th century that have led to land transformation in central Texas

Sesn1 is a novel gene for left-right asymmetry and mediating nodal signaling.

Remarkable progress has been made in understanding the molecular mechanisms underlying left-right asymmetry in vertebrate animal models but little is known on left-right axis formation in humans. Previously, we identified SESN1 (also known as PA26) as a candidate gene for heterotaxia by positional cloning of the breakpoint regions of a de novo translocation in a heterotaxia patient. In this study, we show by means of a zebrafish sesn1-knockdown model that Sesn1 is required for normal embryonic left-right determination. In this model, developmental defects and expression data of genes implicated in vertebrate left-right asymmetry indicate a role for Sesn1 in mediating Nodal signaling. In the lateral plate mesoderm, Nodal signaling plays a central role in left-right axis formation in vertebrates and is mediated by FoxH1 transcriptional induction. In line with this, we show that Sesn1 physically interacts with FoxH1 or a FoxH1-containing complex. Mutation analysis in a panel of 234 patients with isolated heterotaxia did not reveal mutations, indicating that these are only exceptional causes of human heterotaxia. In this study, we identify SESN1 as an indispensable gene for vertebrate left-right asymmetry and a new player in mediating Nodal signaling