Molecular Mechanisms of Autophagy Regulation in Plants and Their Applications in Agriculture

Autophagy is a highly conserved cellular process for the degradation and recycling of unnecessary cytoplasmic components in eukaryotes. Various studies have shown that autophagy plays a crucial role in plant growth, productivity, and survival. The extensive functions of plant autophagy have been revealed in numerous frontier studies, particularly those regarding growth adjustment, stress tolerance, the identification of related genes, and the involvement of metabolic pathways. However, elucidation of the molecular regulation of plant autophagy, particularly the upstream signaling elements, is still lagging. In this review, we summarize recent progress in research on the molecular mechanisms of autophagy regulation, including the roles of protein kinases, phytohormones, second messengers, and transcriptional and epigenetic control, as well as the relationship between autophagy and the 26S proteasome in model plants and crop species. We also discuss future research directions for the potential application of autophagy in agriculture.

Internal ammonium excess induces ROS-mediated reactions and causes carbon scarcity in rice

Background: Overuse of nitrogen fertilizers is often a major practice to ensure sufficient nitrogen demand of high–yielding rice, leading to persistent NH4+ excess in the plant. However, this excessive portion of nitrogen nutrient does not correspond to further increase in grain yields. For finding out the main constraints related to this phenomenon, the performance of NH4+ excess in rice plant needs to be clearly addressed beyond the well-defined root growth adjustment. The present work isolates an acute NH4+ excess condition in rice plant from causing any measurable growth change and analyses the initial performance of such internal NH4+ excess. Results: We demonstrate that the acute internal NH4+ excess in rice plant accompanies readily with a burst of reactive oxygen species (ROS) and initiates the downstream reactions. At the headstream of carbon production, photon caption genes and the activity of primary CO2 fixation enzymes (Rubisco) are evidently suppressed, indicating a reduction in photosynthetic carbon income. Next, the vigorous induction of glutathione transferase (GST) genes and enzyme activities along with the rise of glutathione (GSH) production suggest the activation of GSH cycling for ROS cleavage. Third, as indicated by strong induction of glycolysis / glycogen breakdown related genes in shoots, carbohydrate metabolisms are redirected to enhance the production of energy and carbon skeletons for the cost of ROS scavenging. As the result of the development of these defensive reactions, a carbon scarcity would accumulatively occur and lead to a growth inhibition. Finally, a sucrose feeding cancels the ROS burst, restores the activity of Rubisco and alleviates the demand for the activation of GSH cycling. Conclusion: Our results demonstrate that acute NH4+ excess accompanies with a spontaneous ROS burst and causes carbon scarcity in rice plant. Therefore, under overuse of N fertilizers carbon scarcity is probably a major constraint in rice plant that limits the performance of nitrogen.

Changes in resource partitioning between and within organs support growth adjustment to neighbor proximity in Brassicaceae seedlings

In shade-intolerant plants, the perception of proximate neighbors rapidly induces architectural changes resulting in elongated stems and reduced leaf size. Sensing and signaling steps triggering this modified growth program have been identified. However, the underlying changes in resource allocation that fuel stem growth remain poorly understood. Through 14CO2 pulse labeling of Brassica rapa seedlings, we show that perception of the neighbor detection signal, low ratio of red to far-red light (R:FR), leads to increased carbon allocation from the major site of photosynthesis (cotyledons) to the elongating hypocotyl. While carbon fixation and metabolite levels remain similar in low R:FR, partitioning to all downstream carbon pools within the hypocotyl is increased. Genetic analyses using Arabidopsis thaliana mutants indicate that low-R:FR–induced hypocotyl elongation requires sucrose transport from the cotyledons and is regulated by a PIF7-dependent metabolic response. Moreover, our data suggest that starch metabolism in the hypocotyl has a growth-regulatory function. The results reveal a key mechanism by which metabolic adjustments can support rapid growth adaptation to a changing environment.

Feeling the force: how pollen tubes deal with obstacles

HighlightPollen tubes literally feel their way through their environment to avoid obstacles as they deliver male gametes to the ovule. We measured their force sensitivity to understand this remarkable behavior.AbstractPhysical forces are involved in the regulation of plant development and morphogenesis by translating mechanical stress into the modification of physiological processes, which, in turn, can affect cellular growth. Pollen tubes are tip-growing cells that provide an ideal system to study processes induced by exposure to mechanical stress. We combined a lab-on-a-chip device with cellular force microscopy to mimic and quantify the forces that are involved in pollen tube navigation upon confronting mechanical obstacles. Several stages of obstacle avoidance were identified, including force perception, growth adjustment, and penetration. We have experimentally determined the perceptive force, which is the force threshold at which the pollen tube senses the obstacle, for Lilium longiflorum and Arabidopsis thaliana. In addition, we provide evidence that pollen tubes are capable of penetrating narrow gaps by increasing turgor pressure. Taken together, our data indicate that pollen tubes sense physical barriers and actively adjust their growth behavior to overcome them.

Person of the Month: Erik Erikson (1902-1994)

Erik Homburger Erikson was a German-born American developmental psychologist and psychoanalyst who pioneered in the world of child psychology by giving his development theory with his ‘eight psychosocial stages’. He was born in Frankfurt in unusual circumstances in which his mother did not conceive him through her husband but he never got to know who his biological father was. It is said that the history of his birth is something that triggered the need in him to pursue the concept of identity and it is how he gave the world the psychological term ‘identity crisis’, a major contribution to the world of psychology and psychoanalysis. He grew up in Germany and came in contact with the world of psychoanalysis when he met Sigmund Freud’s daughter Anna Freud. He studied psychoanalysis at the Vienna Psychoanalytic Institute but Nazi invasion of Germany led to his emigration to America. In America, Erikson found a wide scope to practice psychoanalysis on children in Boston and worked at various medical institutes, including the Harvard University and California University. He studied the psychology of children from various social structures, environments, emotional and psychological issues and compiled his observations in the most prominent book of his career, ‘Childhood and Society’. Erikson is also credited with being one of the originators of Ego psychology, which stressed the role of the ego as being more than a servant of the id. According to Erikson, the environment in which a child lived was crucial to providing growth, adjustment, a source of self-awareness and identity. Erikson won a Pulitzer Prize and a U.S. National Book Award in category Philosophy and Religion for Gandhi’s Truth (1969), which focused more on his theory as applied to later phases in the life cycle.

Forecasting Demand: Development of a Fuzzy Growth Adjusted Holt-Winters Approach

Irrespective of the type of items manufactured by an industry, environment is now becoming progressively more and more competitive than the past few decades. To sustain in this severe competition, companies have no choice but to manage their operations optimally and in this respect the importance of more accurate demand prediction cannot be exaggerated. This research presents a forecasting approach tailoring the multiplicative Holt-Winters method with growth adjustment through incorporation of fuzzy logic. The growth parameter of the time series values is adjusted with the conventional Holt-Winters method and tested for predicting the real-life demand of transformer tank experienced by a local company. The result obtained by applying the new approach shows a significant improvement in the accuracy of the forecasted demand and sheds light on further enhancement of the proposed method by optimizing other time series parameters through fuzzy logic application for possible application in prediction of demand having trend, seasonal and cyclical changes.