Land plants are considered monophyletic, descending from a single successful colonization of land by an aquatic algal ancestor. The ability to survive dehydration to the point of desiccation is a key adaptive trait enabling terrestrialization. In extant land plants, desiccation tolerance depends on the action of the hormone abscisic acid (ABA) that acts through a receptor-signal transduction pathway comprising a PYRABACTIN RESISTANCE 1-like (PYL)–PROTEIN PHOSPHATASE 2C (PP2C)–SNF1-RELATED PROTEIN KINASE 2 (SnRK2) module. Early-diverging aeroterrestrial algae mount a dehydration response that is similar to that of land plants, but that does not depend on ABA: Although ABA synthesis is widespread among algal species, ABA-dependent responses are not detected, and algae lack an ABA-binding PYL homolog. This raises the key question of how ABA signaling arose in the earliest land plants. Here, we systematically characterized ABA receptor-like proteins from major land plant lineages, including a protein found in the algal sister lineage of land plants. We found that the algal PYL-homolog encoded by Zygnema circumcarinatum has basal, ligand-independent activity of PP2C repression, suggesting this to be an ancestral function. Similarly, a liverwort receptor possesses basal activity, but it is further activated by ABA. We propose that co-option of ABA to control a preexisting PP2C-SnRK2-dependent desiccation-tolerance pathway enabled transition from an all-or-nothing survival strategy to a hormone-modulated, competitive strategy by enabling continued growth of anatomically diversifying vascular plants in dehydrative conditions, enabling them to exploit their new environment more efficiently.

Despite world food production keeping pace with population growth because of the Green Revolution, the United Nations (UN) State of Food Security and Nutrition in the World 2022 Report indicates that the number of people affected by hunger has increased to 828 million with 29.3% of the global population food insecure, and 22% of children under five years of age stunted. Many more have low-quality, unhealthy diets and micronutrient deficiencies leading to obesity, diabetes, and other diet-related non-communicable diseases. Additionally, current agro-food systems significantly impact the environment and the climate, including soil and water resources. Frequent natural disasters resulting from climate change, pandemics, and conflicts weaken food systems and exacerbate food insecurity worldwide. In this review, we outline the current knowledge in alternative agricultural practices for achieving sustainability as well as policies and practices that need to be implemented for an equitable distribution of resources and food for achieving several goals in the UN 2030 Agenda for Sustainable Development. According to the UN Intergovernmental Panel on Climate Change, animal husbandry, particularly ruminant meat and dairy, accounts for a significant proportion of agricultural greenhouse gas (GHG) emissions and land use but contributes only 18% of food energy. In contrast, plant-based foods, particularly perennial crops, have the lowest environmental impacts. Therefore, expanding the cultivation of perennials, particularly herbaceous perennials, to replace annual crops, fostering climate-smart food choices, implementing policies and subsidies favoring efficient production systems with low environmental impact, empowering women, and adopting modern biotechnological and digital solutions can help to transform global agro-food systems toward sustainability. There is growing evidence that food security and adequate nutrition for the global population can be achieved using climate-smart, sustainable agricultural practices, while reducing negative environmental impacts of agriculture, including GHG emissions.

The process of apical dominance by which the apical bud/shoot tip of the plant inhibits the outgrowth of axillary buds located below has been studied for more than a century. Different approaches were used over time with first the physiology era, the genetic era, and then the multidisciplinary era. During the physiology era, auxin was thought of as the master regulator of apical dominance acting indirectly to inhibit bud outgrowth via unknown secondary messenger(s). Potential candidates were cytokinin (CK) and abscisic acid (ABA). The genetic era with the screening of shoot branching mutants in different species revealed the existence of a novel carotenoid-derived branching inhibitor and led to the significant discovery of strigolactones (SLs) as a novel class of plant hormones. The re-discovery of the major role of sugars in apical dominance emerged from modern physiology experiments and involves ongoing work with genetic material affected in sugar-signalling. As crops and natural selection rely on the emergent properties of networks such as this branching network, future work should explore the whole network, the details of which are critical but not individually sufficient to solve the wicked problems of sustainable food supply and climate change.