Cell-autonomously controlled ground tissue initiation by auxin in early Arabidopsis embryo ($)
MONOPTEROS is an auxin-response factor (ARF) that is necessary for root formation during early embryogenesis. Its activity is modulated by BODENLOS (BDL), an Aux/IAA protein that is degraded in the presence of auxin. Möller et al. investigated the transcriptional targets of MP in very early embryos through the cell-specific expression of a stabilized BDL protein (bdl), which leads to a decrease in expression level of MP targets. The authors showed that MP targets include auxin-regulated genes and several transcription factors. Furthermore, they identified several MP targets that are crucial for ground tissue establishment, and showed that MP acts cell-autonomously in the specification of ground tissue and vascular tissue and that tissue initiation and tissue patterning can be regulated separately. Proc. Natl. Acad. Sci. 10.1073/pnas.1616493114
The transcriptional response to auxin depends in large part on the interactions between ARF transcription factors and the Aux/IAA transcription inhibitors that interact with them. The crucial role of auxin in embryo patterning is revealed by the embryo patterning defects observed in mutants of ARF and Aux/IAA proteins as well as auxin synthesis and transport mutants. Mironova et al. review recent research into the role of auxin in embryo development, focusing on mathematical and structural models of auxin signaling, and particularly how a better understanding of the interactions amongst and between ARFs and Aux/IAA proteins enhances modeling efforts. Trends Plant Sci. 
In leaf mesophyll cells, some of the sugars produced by photosynthesis are stored as transitory starch, which is then broken down to provide the cells with energy during the night. Recent advances in imaging and staining and the use of mutants have enabled the pattern of accumulation of transitory starch in guard cells to be determined. Santelia and Lunn review these new insights and the special role of starch catabolism products (including malate) in stomatal opening in the light. The authors conclude, “Our aim in this review has been to highlight the exciting recent advances in our understanding of guard cell metabolism, with the hope of persuading young researchers to fall in love with stomata, and take up the challenge to explore their fascinating biology.” Plant Physiol. 
Although angiosperms are the dominant autotrophs in most parts of the world, their evolutionary origins remain somewhat mysterious. Herendeen et al. review the earliest evidence for angiosperms from the Early Cretaceous, and discuss fossil remains from earlier periods (Jurassic, Triassic) that have some angiosperm-like features. They conclude that none of these earlier fossils are unambiguously angiosperms, although they don’t rule out the possibility that one day a pre-Cretaceous angiosperm fossil will be found. Nature Plants 
In photosynthesis, light energy generates proton motive force (pmf) across the thylakoid membrane. The establishment and maintenance of pmf involves numerous membrane transporters as well as other ions. Szabò and Septea review how various ions (including K+, Na+, Fe2+, Cu+, Mn2+, Ca2+, Cl–) contribute to photosynthetic efficiency, the approximate range of concentrations of each of these ions in various chloroplast compartments, and the transporters that enable them to cross membranes. The impact of the ion transportome on non-photochemical quenching (NPQ) is also discussed. J. Exp. Bot. 
Nature journal published a special “Plant Insights” section featuring several excellent reviews. Zipfel and Oldroyd review Plant signalling in symbiosis and immunity (
The economy of living cells includes energy production, energy utilization, and energy storage. Thus, a plant’s energy budget must connect the decision to produce lipids (for energy storage) with its overall energy status. Energy sensor kinases, such as KIN10 and KIN11 in Arabidopsis thaliana, are key transcriptional regulators that integrate energy and stress signaling networks (reviewed in 
Over the past several decades, the amount of maize produced in the US Midwestern “Corn Belt” has been rising steadily. In order to accurately predict future grain yields, the factors that contribute to these recent yield increases must be identified. Tollenaar et al. found that more than a quarter (27%) of recent US maize yield increases are a consequence of “solar brightening” – an increase in the amount of light reaching the Earth’s surface in these growing regions. Solar brightening and dimming are affected by clouds but also by air quality. In other parts of the world, declining air quality has led to solar dimming. The authors argue that the beneficial impacts on grain yield should be considered when calculating the costs associated with efforts to protect air quality, and also that the effect of solar brightening is not likely to continue to increase, making the case that genetic sources of yield improvement will be even more important for future yield increases. Nature Climate Change 
The “Law of the Minimum” put forth by Justus von Liebig states that the most limiting nutrient governs plant growth. Although there is evidence in some conditions that increasing atmospheric CO2 levels can enhance plant growth, this only holds true under conditions in which CO2 is limiting growth. Ellsworth et al. found no productivity gains in mature eucalypt forest growing on phosphate-poor soils when CO2 levels were raised. When phosphate fertilizer was added and so growth was no longer P- limited, they observed a growth enhancement with elevated CO2. These results demonstrate the need to consider the availability of soil nutrients when forecasting plant responses to elevated CO2. Nature Climate Change