The molecular mechanism of plasma membrane H+-ATPases in plant responses to abiotic stress

Plasma membrane H⁺-ATPases (PM H⁺-ATPases) are critical proton pumps that export protons from the cytoplasm to the apoplast. The resulting proton gradient and difference in electrical potential energize various secondary active transport events. PM H⁺-ATPases play essential roles in plant growth, development, and stress responses. In this review, we focus on recent studies of the mechanism of PM H⁺-ATPases in response to abiotic stresses in plants, such as salt and high pH, temperature, drought, light, macronutrient deficiency, acidic soil and aluminum stress, as well as heavy metal toxicity. Moreover, we discuss remaining outstanding questions about how PM H⁺-ATPases contribute to abiotic stress responses.

SAUR Proteins as Effectors of Hormonal and Environmental Signals in Plant Growth

The plant hormone auxin regulates numerous aspects of plant growth and development. Early auxin response genes mediate its genomic effects on plant growth and development. Discovered in 1987, small auxin up RNAs (SAURs) are the largest family of early auxin response genes. SAUR functions have remained elusive, however, presumably due to extensive genetic redundancy. However, recent molecular, genetic, biochemical, and genomic studies have implicated SAURs in the regulation of a wide range of cellular, physiological, and developmental processes. Recently, crucial mechanistic insight into SAUR function was provided by the demonstration that SAURs inhibit PP2C.D phosphatases to activate plasma membrane (PM) H(+)-ATPases and promote cell expansion. In addition to auxin, several other hormones and environmental factors also regulate SAUR gene expression. We propose that SAURs are key effector outputs of hormonal and environmental signals that regulate plant growth and development.