The Role of bZIP Transcription Factors in Green Plant Evolution: Adaptive Features Emerging from Four Founder Genes

BACKGROUND: Transcription factors of the basic leucine zipper (bZIP) family control important processes in all eukaryotes. In plants, bZIPs are regulators of many central developmental and physiological processes including photomorphogenesis, leaf and seed formation, energy homeostasis, and abiotic and biotic stress responses. Here we performed a comprehensive phylogenetic analysis of bZIP genes from algae, mosses, ferns, gymnosperms and angiosperms. METHODOLOGY/PRINCIPAL FINDINGS: We identified 13 groups of bZIP homologues in angiosperms, three more than known before, that represent 34 Possible Groups of Orthologues (PoGOs). The 34 PoGOs may correspond to the complete set of ancestral angiosperm bZIP genes that participated in the diversification of flowering plants. Homologous genes dedicated to seed-related processes and ABA-mediated stress responses originated in the common ancestor of seed plants, and three groups of homologues emerged in the angiosperm lineage, of which one group plays a role in optimizing the use of energy. CONCLUSIONS/SIGNIFICANCE: Our data suggest that the ancestor of green plants possessed four bZIP genes functionally involved in oxidative stress and unfolded protein responses that are bZIP-mediated processes in all eukaryotes, but also in light-dependent regulations. The four founder genes amplified and diverged significantly, generating traits that benefited the colonization of new environments

An Sp1 transcription factor coordinates caspase-dependent and -independent apoptotic pathways

During animal development, the proper regulation of apoptosis requires the precise spatial and temporal execution of cell-death programs, which can include both caspase-dependent and caspase-independent pathways. Although the mechanisms of caspase-dependent and -independent cell killing have been examined extensively, how these pathways are coordinated within a single cell that is fated to die is unknown. Here we show that the Caenorhabditis elegans Sp1 transcription factor SPTF-3 specifies the programmed cell deaths of at least two cells—the sisters of the pharyngeal M4 motor neuron and the AQR sensory neuron—by transcriptionally activating both caspase-dependent and -independent apoptotic pathways. SPTF-3 directly drives the transcription of the gene egl-1, which encodes a BH3-only protein that promotes apoptosis through the activation of the CED-3 caspase. In addition, SPTF-3 directly drives the transcription of the AMP-activated protein kinase-related gene pig-1, which encodes a protein kinase and functions in apoptosis of the M4 sister and AQR sister independently of the pathway that activates CED-3. Thus, a single transcription factor controls two distinct cell-killing programs that act in parallel to drive apoptosis. Our findings reveal a bivalent regulatory node for caspase-dependent and -independent pathways in the regulation of cell-type-specific apoptosis. We propose that such nodes might act as features of a general mechanism for regulating cell-type-specific apoptosis and could be therapeutic targets for diseases involving the dysregulation of apoptosis through multiple cell-killing mechanisms.Howard Hughes Medical Institut

Key issues in the conservation of the Australian coastal archaeological record: natural and human impacts

Australia has an extensive coastline extending over 60,000 km through diverse tropical and temperate environments. Indigenous archaeological sites are found along this coastline from the time of earliest settlement at least 50,000 years ago. However, Pleistocene sites are rare owing largely to the destructive impacts of sea-level change associated with the end of the last ice age around 10,000 years ago. After this sites are more numerous but there is variability around the coastline due to the impact of a range of both natural and human factors. Here we focus on six key issues impacting on the development and conservation of coastal archaeological deposits: sea-levels, climate change, cyclones, storms, tsunamis and contemporary human impacts. A number of examples of these impacts are discussed from across Australia. Managing and monitoring of sites has been limited in Australia and geoindicators are discussed as a means of developing a long-term measurement of continuing impacts