Search for: All records

Abstract Understanding crop plants responses to abiotic stress is increasingly important in this changing climate. We asked experts how discoveries in Arabidopsis thaliana have translated into advancements in abiotic crop stress resilience. The theme is that core regulatory networks identified in Arabidopsis are conserved in crops, but the molecular regulation varies among species. For cold tolerance, the regulatory framework is conserved, but MAP Kinase signaling promotes degradation of the INDUCER OF DREB1 EXPRESSION transcription factor in Arabidopsis but inhibits it in rice. For hypoxia, manipulation of the oxygen sensing Arg/N-degron pathway discovered in Arabidopsis has improved waterlogging and flood tolerance in barley, maize, wheat, and soybean. For light signaling, overexpression of PHYTOCHROME B reduces shade avoidance, improving yield under dense planting in potato, soybean, and maize. In rice, understanding of nitrogen responsiveness, uptake, and transport in Arabidopsis has inspired engineering of the NRT1 nitrate transceptor to increase yield. Arabidopsis research has provided leads for genetic manipulations that may improve drought resilience in crop species. Growing plants in space generates a complex array of stresses, and Arabidopsis experiments in the space station prepare for future development of robust crops as integral components of the life support systems. For environmental regulation of flowering time, the role of the GIGANTEA - CONTANS - FLOWERING LOCUS T module elucidated in Arabidopsis is largely conserved in crop plants, although additional regulators modify short-day responsiveness in rice, soybean, chrysanthemum, and potato. 

Abstract Since its first identification in the 1950s as a regulator of cell division, cytokinin has been linked to many physiological processes in plants, spanning growth and development and various responses to the environment. Studies from the last two and one-half decades have revealed the pathways underlying the biosynthesis and metabolism of cytokinin and have elucidated the mechanisms of its perception and signaling, which reflects an ancient signaling system evolved from two-component elements in bacteria. Mutants in the genes encoding elements involved in these processes have helped refine our understanding of cytokinin functions in plants. Further, recent advances have provided insight into the mechanisms of intracellular and long-distance cytokinin transport and the identification of several proteins that operate downstream of cytokinin signaling. Here, we review these processes through a historical lens, providing an overview of cytokinin metabolism, transport, signaling, and functions in higher plants. 

ABSTRACT Plant immunity activation often results in suppression of plant growth, particularly in the case of constitutive immune activation. We discovered that signaling of the phytohormone cytokinin (CK), known to regulate plant growth through the control of cell division and shoot apical meristem (SAM) activity, can be suppressed by negative crosstalk with the defense phytohormones jasmonic acid (JA), and most evidently, salicylic acid (SA). We show that changing the negative crosstalk of SA on CK signaling in autoimmunity mutants by targeted increase of endogenous CK levels results in plants resistant to pathogens from diverse lifestyles, and relieves suppression of reproductive growth. Moreover, such changes in crosstalk result in a novel reproductive growth phenotype, suggesting a role for defense phytohormones in the SAM, likely through regulation of nitrogen response and cellular redox status. Our data suggest that targeted phytohormone crosstalk engineering can be used to achieve increased reproductive growth and pathogen resistance. SIGNIFICANCE STATEMENTPlants constantly integrate environmental stimuli with developmental programs to optimize their growth and fitness. Excessive activation of the plant immune system often leads to decreased plant growth, a process known as the growth-defense tradeoff. Here, we adapted phytohormone levels in Arabidopsis reproductive tissues of autoimmunity mutants to change phytohormonal crosstalk and diminish the growth tradeoff, resulting in increased broad resistance to pathogens and decreased growth suppression. Similar approaches to phytohormone crosstalk engineering could be used in different contexts to achieve outcomes of higher plant stress resilience and yield. 

Although gibberellic acid (GA) is widely used in agriculture, it is unclear whether exogenous GA makes aphid-infested, mycorrhizal plants more susceptible to herbivory. This study investigates the role of GA in modulating defenses in barrel medic plants (Medicago truncatula) that are infested with pea aphids (Acyrthosiphon pisum) and colonized by the beneficial symbiont Rhizophagus intraradices. Mock- and R. intraradices-inoculated potted plants were grown in a topsoil: sand mix for 42 days and were treated with GA or solvent. Subsequently, plants were exposed to herbivory or no aphid herbivory for 36 h and 7 days. Afterwards, plant growth parameters, aphid fitness, and foliar phytohormone concentrations were measured. The results revealed that GA regulates plant defenses during arbuscular mycorrhizal (AM) fungus–plant–aphid interactions as aphids that fed for 7 days on mycorrhizal, GA-untreated plants weighed more than those that fed on mycorrhizal, GA-treated plants. No major differences were detected in phytohormone levels at 36 h. Overall, mycorrhizal plants showed more shoot biomass compared to non-mycorrhizal controls. The arbuscule density and fungal biomass of R. intraradices were not altered by exogenous GA and aphid herbivory based on molecular markers. This study indicates that exogenous GA may help reduce aphid fitness when feeding on mycorrhizal plants.