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Auxin is perceived by a co-receptor complex that contains a TIR1 F-box protein and an Aux/IAA transcriptional repressor. The combinatorial diversity of auxin co-receptor complexes and their distinct spectra of affinities offer a means to tune plant cell sensitivity to a wide range of auxin concentrations. The plant hormone auxin regulates virtually every aspect of plant growth and development. Auxin acts by binding the F-box protein transport inhibitor response 1 (TIR1) and promotes the degradation of the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) transcriptional repressors. Here we show that efficient auxin binding requires assembly of an auxin co-receptor complex consisting of TIR1 and an Aux/IAA protein. Heterologous experiments in yeast and quantitative IAA binding assays using purified proteins showed that different combinations of TIR1 and Aux/IAA proteins form co-receptor complexes with a wide range of auxin-binding affinities. Auxin affinity seems to be largely determined by the Aux/IAA. As there are 6 TIR1/AUXIN SIGNALING F-BOX proteins (AFBs) and 29 Aux/IAA proteins in Arabidopsis thaliana , combinatorial interactions may result in many co-receptors with distinct auxin-sensing properties. We also demonstrate that the AFB5–Aux/IAA co-receptor selectively binds the auxinic herbicide picloram. This co-receptor system broadens the effective concentration range of the hormone and may contribute to the complexity of auxin response.

The plant hormone auxin is thought to provide positional information for patterning during development. It is still unclear, however, precisely how auxin is distributed across tissues and how the hormone is sensed in space and time. The control of gene expression in response to auxin involves a complex network of over 50 potentially interacting transcriptional activators and repressors, the auxin response factors (ARFs) and Aux/IAAs. Here, we perform a large‐scale analysis of the Aux/IAA‐ARF pathway in the shoot apex of Arabidopsis , where dynamic auxin‐based patterning controls organogenesis. A comprehensive expression map and full interactome uncovered an unexpectedly simple distribution and structure of this pathway in the shoot apex. A mathematical model of the Aux/IAA‐ARF network predicted a strong buffering capacity along with spatial differences in auxin sensitivity. We then tested and confirmed these predictions using a novel auxin signalling sensor that reports input into the signalling pathway, in conjunction with the published DR5 transcriptional output reporter. Our results provide evidence that the auxin signalling network is essential to create robust patterns at the shoot apex. Synopsis The plant hormone auxin is a key morphogenetic signal involved in the control of cell identity throughout development. A striking example of auxin action is at the shoot apical meristem (SAM), a population of stem cells generating the aerial parts of the plant. Organ positioning and patterning depends on local accumulations of auxin in the SAM, generated by polar transport of auxin (Vernoux et al , 2010 ). However, it is still unclear how auxin is distributed at cell resolution in tissues and how the hormone is sensed in space and time during development. A complex ensemble of 29 Aux/IAAs and 23 ARFs is central to the regulation of gene transcription in response to auxin (for review, see Leyser, 2006 ; Guilfoyle and Hagen, 2007 ; Chapman and Estelle, 2009 ). Protein–protein interactions govern the properties of this transduction pathway (Del Bianco and Kepinski, 2011 ). Limited interaction studies suggest that, in the absence of auxin, the Aux/IAA repressors form heterodimers with the ARF transcription factors, preventing them from regulating target genes. In the presence of auxin, the Aux/IAA proteins are targeted to the proteasome by an SCF E3 ubiquitin ligase complex (Chapman and Estelle, 2009 ; Leyser, 2006 ). In this process, auxin promotes the interaction between Aux/IAA proteins and the TIR1 F‐box of the SCF complex (or its AFB homologues) that acts as an auxin co‐receptor (Dharmasiri et al , 2005a , 2005b ; Kepinski and Leyser, 2005 ; Tan et al , 2007 ). The auxin‐induced degradation of Aux/IAAs would then release ARFs to regulate transcription of their target genes. This includes activation of most of the Aux/IAA genes themselves, thus establishing a negative feedback loop (Guilfoyle and Hagen, 2007 ). Although this general scenario provides a framework for understanding gene regulation by auxin, the underlying protein–protein network remains to be fully characterized. In this paper, we combined experimental and theoretical analyses to understand how this pathway contributes to sensing auxin in space and time (Figure 1 ). We first analysed the expression patterns of the ARFs , Aux/IAAs and TIR1 / AFBs genes in the SAM. Our results demonstrate a general tendency for most of the 25 ARFs and Aux/IAAs detected in the SAM: a differential expression with low levels at the centre of the meristem (where the stem cells are located) and high levels at the periphery of the meristem (where organ initiation takes place). We also observed a similar differential expression for TIR1/AFB co‐receptors. To understand the functional significance of the distribution of ARFs and Aux/IAAs in the SAM, we next investigated the global structure of the Aux/IAA‐ARF network using a high‐throughput yeast two‐hybrid approach and uncover a rather simple topology that relies on three basic generic features: (i) Aux/IAA proteins interact with themselves, (ii) Aux/IAA proteins interact with ARF activators and (iii) ARF repressors have no or very limited interactions with other proteins in the network. The results of our interaction analysis suggest a model for the Aux/IAA‐ARF signalling pathway in the SAM, where transcriptional activation by ARF activators would be negatively regulated by two independent systems, one involving the ARF repressors, the other the Aux/IAAs. The presence of auxin would remove the inhibitory action of Aux/IAAs, but leave the ARF repressors to compete with ARF activators for promoter‐binding sites. To explore the regulatory properties of this signalling network, we developed a mathematical model to describe the transcriptional output as a function of the signalling input that is the combinatorial effect of auxin concentration and of its perception. We then used the model and a simplified view of the meristem (where the same population of Aux/IAAs and ARFs exhibit a low expression at the centre and a high expression in the peripheral zone) for investigating the role of auxin signalling in SAM function. We show that in the model, for a given ARF activator‐to‐repressor ratio, the gene induction capacity increases with the absolute levels of ARF proteins. We thus predict that the differential expression of the ARF s generates differences in auxin sensitivities between the centre (low sensitivity) and the periphery (high sensitivity), and that the expression of TIR1/AFB participates to this regulation (prediction 1). We also use the model to analyse the transcriptional response to rapidly changing auxin concentrations. By simulating situations equivalent either to the centre or the periphery of our simplified representation of the SAM, we predict that the signalling pathway buffers its response to the auxin input via the balance between ARF activators and repressors, in turn generated by their differential spatial distributions (prediction 2). To test the predictions from the model experimentally, we needed to assess both the input (auxin level and/or perception) and the output (target gene induction) of the signalling cascade. For measuring the transcriptional output, the widely used DR5 reporter is perfectly adapted (Figure 5 ) (Ulmasov et al , 1997 ; Sabatini et al , 1999 ; Benkova et al , 2003 ; Heisler et al , 2005 ). For assaying pathway input, we designed DII‐VENUS, a novel auxin signalling sensor that comprises a constitutively expressed fusion of the auxin‐binding domain (termed domain II or DII) (Dreher et al , 2006 ; Tan et al , 2007 ) of an IAA to a fast‐maturating variant of YFP, VENUS (Figure 5 ). The degradation patterns from DII‐VENUS indicate a high auxin signalling input both in flower primordia and at the centre of the SAM. This is in contrast to the organ‐specific expression pattern of DR5::VENUS (Figure 5 ). These results indicate that the signalling pathway limits gene activation in response to auxin at the meristem centre and confirm the differential sensitivity to auxin between the centre and the periphery (prediction 1). We further confirmed the buffering capacities of the signalling pathway (prediction 2) by carrying out live imaging experiments to monitor DII‐VENUS and DR5::VENUS expression in real time (Figure 5 ). This analysis reveals the presence of important temporal variations of DII‐VENUS fluorescence, while DR5::VENUS does not show such global variations. Our approach thus provides evidence that the Aux/IAA‐ARF pathway has a key role in patterning in the SAM, alongside the auxin transport system. Our results illustrate how the tight spatio‐temporal regulation of both the distribution of a morphogenetic signal and the activity of the downstream signalling pathway provides robustness to a dynamic developmental process. We provide a comprehensive expression map of the different genes (TIR1/AFBs, ARFs and Aux/IAAs) involved in the signalling pathway regulating gene transcription in response to auxin in the shoot apical meristem (SAM). We demonstrate a relatively simple structure of this pathway using a high‐throughput yeast two‐hybrid approach to obtain the Aux/IAA‐ARF full interactome. The topology of the signalling network was used to construct a model for auxin signalling and to predict a role for the spatial regulation of auxin signalling in patterning of the SAM. We used a new sensor to monitor the input in the auxin signalling pathway and to confirm the model prediction, thus demonstrating that auxin signalling is essential to create robust patterns at the SAM.

Real estate developers typically assess potential projects using feasibility analyses and industry-standard heuristics, which include capital costs, return on costs, and a subjective risk measure. This study explores real estate developers’ decision-making practices in selecting hurdle rates and common feasibility analysis techniques, surveying 225 Australian and New Zealand developers. The main findings are that most developers use specific ‘go/no-go’ hurdle rate mechanisms irrespective of primary real estate type, with the majority using margin on development cost (MDC) or internal rate of return (IRR); the boundaries between traditional speculative development and real estate investment through the use of securitization methods have become blurred; many developers use both quantitative metrics, with qualitative methods and specific structural checks to manage the risks involved; and the two most frequent methods of determining site value prior to acquisition are the residual land value and discounted cash flow methods. Most place a heavy reliance on industry-accepted heuristics and do not have a predetermined process and method for altering or adapting the chosen hurdle rates and benchmarks. This research provides a contribution to property development practice from the Antipodean perspective which until now has been more focused on the UK view, enabling more generalized application internationally.

Australia’s housing affordability crisis has deepened despite extensive policy intervention, with the private rental sector experiencing unprecedented pressure. This study proposes that affordable housing should guarantee low and moderate-income households their fundamental right to access secure and safe dwellings, enabling these households to meet essential needs and maintain quality of life without enduring housing stress. Despite significant public investment, a critical housing shortage persists across the nation with a need to build 640,000 homes annually. This crisis is exacerbated by ineffective public–private–community partnerships (PPCP) and the absence of a unified national housing policy. This study critically examines the NRAS to understand why market-based interventions have consistently fallen short of addressing housing affordability challenges. Through empirical analysis of 31 in-depth interviews with senior stakeholders across public, private and community sectors, this research identifies five systemic barriers: definitional inconsistencies in affordable housing policy; inflexible strategic frameworks; misaligned investment incentives; geographical inequities in resource allocation; and fragmented governance structures. The study introduces the Personal and Collective Will in Policy Implementation (PaCWiPI) framework as an innovative approach integrating Maslow’s Hierarchy of Needs with Henderson’s Poverty Line metrics. Our findings demonstrate that effective housing policy requires a fundamental shift from rigid, standardised approaches towards adaptive frameworks that are responsive to diverse market conditions. This research advances housing policy scholarship by providing empirical evidence of implementation barriers while offering practical recommendations for future initiatives, relevant to the current Housing Australia Future Fund and other regionally-related housing policies.

PurposeThe purpose of this study is to analyse the current relationships between developer characteristics in terms of dominant property type (residential, commercial, retail, industrial, tourism, “other”), ownership (publicly listed, publicly unlisted, private, government), organisational structure (speculative-trader, investor developers, development managers) and size (small, medium, large) in the frequency of use and required minimum value of hurdle rate metrics.Design/methodology/approachA questionnaire survey of 225 Australian and New Zealand trader developers, development managers, investors, valuers, fund managers and government/charities/other relating to the feasibility practices of different types of Australia/New Zealand property development companies.Findings(1) Residential dominant developers are more likely to use margin on development cost (MDC) required to have a higher minimum internal rate of return (IRR) percentage; (2) investor developers are more likely to use the payback period as a hurdle rate, and specific hurdle rates as a part of a go/no-go decision; (3) trader developers adopt a higher percentage of IRR and deviate further from accepted financial theory in hurdle rate selection; and (4) national property development organisations in multiple geographic regions use qualitative frameworks more as a decision-making process and use MDC less as a hurdle rate.Practical implicationsThe study is limited to a sample of property practitioners working in Australia/New Zealand at the time of data collection in 2016 and, further empirical research is needed spatially and temporally to determine the extent of the findings. Further research is also needed with small- to medium-sized development organisations' on the extent to which they should use different metrics in project selection and for an improved understanding of the technical and attitudinal difficulties facing their current adoption.Originality/valueFirst study to examine the feasibility practices of different types of Australia/New Zealand property developers.

PurposeThe purpose is to examine the risk management processes and methods used in determining project feasibility in the early stages of the property development process by Australia/New Zealand property developers, including Monte Carlo simulation, Bayesian models and real option theory embedded in long-term property development and investment decision-making as instruments for providing flexibility and managing risk, uncertainty and change.Design/methodology/approachA questionnaire survey of 225 Australian and New Zealand trader developers, development managers, investors, valuers, fund managers and government/charities/other relating to Australia/New Zealand property development companies' decision-making processes in the early stages of the development process prior to site acquisition or project commencement – the methods used and confidence in their organisations' ability to both identify and manage the risks involved.FindingsFew of the organisations sampled use sophisticated methods; those organisations that are more likely to use such methods for conducting risk analysis include development organisations that undertake large projects, use more risk analysis methods and have more layers in their project approval process. Decision-makers have a high level of confidence in their organisation's ability to both identify and manage the risks involved, although this is not mirrored in their actual risk management processes. Although the majority of property developers have a risk management plan, less than half have implemented it, and a third need improvement.Practical implicationsProperty development organisations should incorporate more modern and sophisticated models of risk analysis to determine the uncertainty of, and risk in, a change of input variables in their financial viability appraisals. Practical application includes using such multiple techniques as what-if scenarios and probability analysis into feasibility processes and utilise these specific techniques in the pre-acquisition stages of the property development process and, specifically, in the site acquisition process to support decision-making, including a live risk register and catalogue of risks, including identification of and plans for mitigation of project risks, as a form of risk management.Originality/valueFirst study to examine the extent of the decision-making methods used by property developers in the pre-acquisition stage of the development process.

Purpose - The purpose of this paper is to consider some of the approaches which have been developed to bring forward awareness of the role of heritage and its significance in reducing the use of carbon incurred by the creation of new structures.Design methodology approach - The approach adopted is to look at the emergence and dissemination of these issues through published literature including professional standards and guidelines for the management and valuation of historic property and also to consider the practice of heritage management and assessment in Western Australia.Findings - The paper finds that Australia has a well-developed system of heritage management but has been slow to adapt to its responsibilities under international treaties in the area of sustainable practices in the property field but that there is evidence of progress to improve the situation. Whilst the overall picture of the impact of heritage listing on property value remains clouded, and arguments for both positive and negative impacts are evident from the many perspectives researchers have considered, the sustainable use of resources is one which is currently receiving more attention in professional and academic circles.Research limitations implications - The predominant focus of this paper is from an Australian perspective but with reference to the UK context.Originality value - The contribution of this paper is that, by drawing attention to the value of built heritage as an expression of cultural worth, the demand for new structures can be constrained to some extent by reuse of existing buildings, resulting in more sustainable practices. This environmental view of heritage property may result in its being more favoured as an investment asset in the future due to its smaller carbon footprint than more recent, or potential replacement, structures.

Purpose - The purpose of this paper is to deepen understanding of what is working and what is not working within green workplace environments. The paper examines management and employee perceptions of their experiences of working in green workplace environments and assesses the effectiveness of such places.Design methodology approach - Being the second stage of a longitudinal study, this paper relies on a data set derived from its survey of 31 management and 351 employee respondents occupying Green Building Council Australia Green Star-rated offices for more than 12 months.Findings - The green workplace is a great place to be, at least most of the time, but there is a discrepancy between the views of management who see greater benefits of the green workplace than their employees.Research limitations implications - By focussing on green buildings, there is no control to establish a benchmark. Hence, the next stage of the research is a comparable study of a non-green data sample. Also to be tested is - whilst managers and employees overall report satisfaction with their green workplace, what is the norm?Practical implications - The findings are useful for green building industry practitioners and for building owners and managers to maximise the benefits of owning and occupying green buildings by highlighting areas that may require particular attention in order to get it right. The results are particularly useful to support targeted efforts to meet the environmental aspects of the workspace needs of employees. This study aims to assist industry practitioners, owner and managers to learn from the experience of current occupiers and thereby assist the design and space management of office space in the future where such considerations will become increasingly important given the international concerns for improved resource management.Originality value - With international applicability, a large sample of office space users provides empirical evidence of what works does not work within the green workplace, i.e. its strengths and weaknesses and provides a good reference point for similar studies in the future, leading to the establishment of clearer, more useful benchmarks of green building occupier satisfaction.

There is a huge unmet demand for affordable housing in Australia, and the severe shortage of such accommodation has led to persistent long term homelessness for many families and individuals. Whilst the shortage is nationwide, the situation is particularly severe in regional Australia and, for indigenous people, their plight is even more extreme. Whilst all Australian states and territories have a statutory responsibility for housing provision, the Australian federal government is also adopting a range of strategies to address this critical situation, with indications of successful outcomes providing hope for long term amelioration of this pernicious problem. Within the context of the partnership framework, this paper reports on an initiative in Alice Springs which is proposing an affordable housing development project catering to the needs of indigenous communities, is environmentally conscious, and provides investment opportunities for the potential partners. This vision is shared by many community-based and non-government organisations as well as by the Australian government, and all parties are very sensitive to the urgent attention demanded by this growing problem. After reviewing economic, environmental, and social indicators framing the need for affordable housing at the national scale, the study applies these metrics to a property in Alice Springs which the current owners, the Anglican Church, are keen to redevelop in a manner consistent with socially responsible outcomes. More specifically, the paper reports detailed proposals for indigenous community housing and applies a financial model to test the financial viability of the proposals. This exercise is not only providing a financial feasibility of the specific proposal and site, but offers an economic model that focuses on all three aspects of sustainability and is of more general potential application for indigenous community housing.