Transcription factor ZmNAC19 promotes embryo development in Arabidopsis thaliana.

KEY MESSAGE: Overexpression of ZmNAC19, a NAC transcription factor gene from maize, improves embryo development in transgenic Arabidopsis. NAC proteins are plant-specific transcription factors that are involved in multiple aspects of plant growth, development and stress response. Although functions of many NAC transcription factors have been elucidated, little is known about their roles in seed development. In this study, we report the function of a maize NAC transcription factor ZmNAC19 in seed development. ZmNAC19 is highly expressed in embryos of developing maize seeds. ZmNAC19 localizes to nucleus and exhibits transactivation activity in yeast cells. Overexpression of ZmNAC19 in Arabidopsis significantly increases seed size and seed yield. During 3 to 7 days after flowering, embryos of ZmNAC19-overexpression Arabidopsis lines developed faster compared to Col-0, while no visible differences were detected for their endosperms. Furthermore, overexpression of ZmNAC19 in Arabidopsis leads to increased transcription levels of two embryo development-related genes YUC1 and RGE1, and several elements proven to be binding sites of NAC transcription factors were observed in promoters of these two genes. Taken together, these results suggest that ZmNAC19 acts as a positive regulator in plant embryo development.

A Gate-Tunable Ambipolar Quantum Phase Transition in a Topological Excitonic Insulator.

Coulomb interactions among electrons and holes in 2D semimetals with overlapping valence and conduction bands can give rise to a correlated insulating ground state via exciton formation and condensation. One candidate material in which such excitonic state uniquely combines with non-trivial band topology are atomic monolayers of tungsten ditelluride (WTe2 ), in which a 2D topological excitonic insulator (2D TEI) forms. However, the detailed mechanism of the 2D bulk gap formation in WTe2 , in particular with regard to the role of Coulomb interactions, has remained a subject of ongoing debate. Here, it shows that WTe2 is susceptible to a gate-tunable quantum phase transition, evident from an abrupt collapse of its 2D bulk energy gap upon ambipolar field-effect doping. Such gate tunability of a 2D TEI, into either n- and p-type semimetals, promises novel handles of control over non-trivial 2D superconductivity with excitonic pairing.

Performance benchmarking of an ultra-low vibration laboratory to host a commercial millikelvin scanning tunnelling microscope.

Ultra-low temperature scanning tunnelling microscopy and spectroscopy (STM/STS) achieved by dilution refrigeration can provide unrivalled insight into the local electronic structure of quantum materials and atomic-scale quantum systems. Effective isolation from mechanical vibration and acoustic noise is critical in order to achieve ultimate spatial and energy resolution. Here, we report on the design and performance of an ultra-low vibration (ULV) laboratory hosting a customized but otherwise commercially available 40 mK STM. The design of the vibration isolation consists of a T-shaped concrete mass block (∼55t), suspended by actively controlled pneumatic springs, and placed on a foundation separated from the surrounding building in a 'room-within-a-room' design. Vibration levels achieved are meeting the VC-M vibration standard at >3 Hz, reached only in a limited number of laboratories worldwide. Measurement of the STM's junction noise confirms effective vibration isolation on par with custom built STMs in ULV laboratories. In this tailored low-vibration environment, the STM achieves an energy resolution of 43µeV (144 mK), promising for the investigation and control of quantum matter at atomic length scales.

Patatin-like phospholipase A-induced alterations in lipid metabolism and jasmonic acid production affect the heat tolerance of Gracilariopsis lemaneiformis.

High temperatures seriously limit the growth and productivity of Gracilariopsis lemaneiformis. By hydrolyzing glycerolipids into lysophospholipids (LPs) and free fatty acids (FFAs), patatin-like phospholipase A (pPLA) plays an important role in stress responses. GlpPLA expression was up-regulated under heat stress, however, the regulation of pPLA in heat tolerance of G. lemaneiformis is unknown. In this study, G. lemaneiformis under heat stress was treated with bromoenololide (BEL), a chemical inhibitor of pPLA, to evaluate the cellular function of pPLA in this species. When pPLA was inhibited through BEL treatment, the sensitivity of G. lemaneiformis to heat stress increased and the biomass and maximum and effective quantum yield of photosystem II decreased. Moreover, BEL treatment resulted in a significant decrease in many lipid molecular species, all of which are mainly composed of 16C, 18C, and 20C fatty acids. Consistently, FFA levels and LPs contents in G. lemaneiformis under BEL treatment showed a significant decrease. The first step in the synthesis of jasmonic acid (JA) is the lipoxygenase (LOX)-mediated oxygenation of linolenic acid (C18:3). BEL treatment decreased JA and C18:3 accumulation and markedly downregulated the expression of GILOX under heat stress. Together, these results indicate that pPLA is closely related to the growth of G. lemaneiformis under heat stress, and pPLA is involved in the lipid metabolism and JA biosynthesis of G. lemaneiformis in response to heat stress. This research broadens the understanding of the heat stress adaptation mechanism of G. lemaneiformis.