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2D carbides and nitrides (MXenes) are widely recognized for their exceptional promise for numerous applications. However, physical property measurements of their individual monolayers remain very limited despite their importance for revealing the intrinsic physical properties of MXenes. The first mechanical and electrical measurements of individual single‐layer flakes of Nb4C3Tx MXene, which are prepared via an improved synthetic method are reported. Characterization of field‐effect transistor devices based on individual single‐layer Nb4C3Tx flakes shows an electrical conductivity of 1024 ± 165 S cm−1, which is two orders of magnitude higher than the previously reported values for bulk Nb4C3Tx assemblies, and an electron mobility of 0.41 ± 0.27 cm2 V−1 s−1. Atomic force microscopy nanoindentation measurements of monolayer Nb4C3Tx membranes yield an effective Young's modulus of 386 ± 13 GPa, assuming a membrane thickness of 1.26 nm. This is the highest value reported for nanoindentation measurements of solution‐processable 2D materials, revealing the potential of Nb4C3Tx as a primary component for various mechanical applications. Finally, the agreement between the mechanical properties of 2D Nb4C3Tx MXene and cubic NbC suggests that the extensive experimental data on bulk carbides could be useful for identifying new MXenes with improved functional characteristics.

SummaryPanicle architecture and seed size are important agronomic traits that directly determine grain yield in rice (Oryza sativa L.). Although a number of key genes controlling panicle architecture and seed size have been cloned and characterized in recent years, their genetic and molecular mechanisms remain unclear. In this study, we identified a mutant that produced panicles with fascicled primary branching and reduced seeds in size. We isolated the underlying CLUSTERED PRIMARY BRANCH 1 (CPB1) gene, a new allele of DWARF11 (D11) encoding a cytochrome P450 protein involved in brassinosteroid (BR) biosynthesis pathway. Genetic transformation experiments confirmed that a His360Leu amino acid substitution residing in the highly conserved region of CPB1/D11 was responsible for the panicle architecture and seed size changes in the cpb1 mutants. Overexpression of CPB1/D11 under the background of cpb1 mutant not only rescued normal panicle architecture and plant height, but also had a larger leaf angle and seed size than the controls. Furthermore, the CPB1/D11 transgenic plants driven by panicle-specific promoters can enlarge seed size and enhance grain yield without affecting other favourable agronomic traits. These results demonstrated that the specific mutation in CPB1/D11 influenced development of panicle architecture and seed size, and manipulation of CPB1/D11 expression using the panicle-specific promoter could be used to increase seed size, leading to grain yield improvement in rice.

The elimination of seed shattering was a crucial event during crop domestication. Improving and fine-tuning the regulation of this process will further enhance grain yield by avoiding seed losses during crop production. In this work, we identified the loss-of-shattering mutant suppression of shattering1 (ssh1) through a screen of mutagenized wild rice (Oryza rufipogon) introgression lines with naturally high shattering. Using the MutMap approach and transformation experiments, we isolated a genetic factor for seed shattering, SSH1, which is an allele of SUPERNUMERARY BRACT (SNB), a gene encoding a plantspecific APETALA2-like transcription factor. A C-to-A point mutation in the ninth intron of SNB altered the splicing of its messenger RNA, causing the reduced shattering of the ssh1 mutant by altering the development of the abscission layer and vascular bundle at the junction between the seed and the pedicel. Our data suggest that SNB positively regulates the expression of two rice REPLUMLESS orthologs, qSH1 and SH5. In addition, the ssh1 mutant had larger seeds and a higher grain weight, resulting from its increased elongation of the glume longitudinal cells. The further identification of favorable SNB alleles will be valuable for improving rice seed shattering and grain yield using molecular breeding strategies.

Inflorescence branching is a key agronomic trait determining rice yield. The primary branch of the ancestral wild rice (Oryza rufipogon Griff.) bears few grains, due to minimal secondary branching. By contrast, Oryza sativa cultivars have been selected to produce large panicles with more secondary branches. Here we showed that the CONTROL OF SECONDARY BRANCH 1 (COS1) gene, which is identical to FRIZZY PANICLE (FZP), plays an important role in the key transition from few secondary branches in wild rice to more secondary branches in domesticated rice cultivars. A 4-bp tandem repeat deletion approximately 2.7 kb upstream of FZP may affect the binding activities of auxin response factors to the FZP promoter, decrease the expression level of FZP and significantly enhance the number of secondary branches and grain yield in cultivated rice. Functional analyses showed that NARROW LEAF 1 (NAL1), a trypsin-like serine and cysteine protease, interacted with FZP and promoted its degradation. Consistently, downregulating FZP expression or upregulating NAL1 expression in the commercial cultivar Zhonghua 17 increased the number of secondary branches per panicle, grain number per panicle and grain yield per plant. Our findings not only provide insights into the molecular mechanism of increasing grain number and yield during rice domestication, but also offer favorable genes for improving the grain yield of rice.

Improving the yield by modifying plant architecture was a key step during crop domestication. Here, we show that a 110-kb deletion on the short arm of chromosome 7 in Asian cultivated rice (Oryza sativa), which is closely linked to the previously identified PROSTRATE GROWTH 1 (PROG1) gene, harbors a tandem repeat of seven zinc-finger genes. Three of these genes regulate the plant architecture, suggesting that the deletion also promoted the critical transition from the prostrate growth and low yield of wild rice (O. rufipogon) to the erect growth and high yield of Asian cultivated rice. We refer to this locus as RICE PLANT ARCHITECTURE DOMESTICATION (RPAD). Further, a similar but independent 113-kb deletion is detected at the RPAD locus in African cultivated rice. These results indicate that the deletions, eliminating a tandem repeat of zinc-finger genes, may have been involved in the parallel domestication of plant architecture in Asian and African rice.

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In this paper, we report on the interaction of Nb2SnC ternary transition metal carbide (MAX phase) with Li ions. Because of the presence of Sn layers, which can undergo alloying reaction with Li, this material may be promising for energy storage. Contrary to most electrodes, the performance of this material improves along with the cycle number; specifically, the capacity increases gradually from 87 mAh g-1 to 150 mAh g-1 at a current density of 500 mA g-1 during 600 charge/discharge cycles. Post-cycling study suggests that the alloying reaction makes the material break into smaller particles, increasing capacity. Since Nb2SnC is just one of many MAX phases, this work lays the foundation for the exploration of the MAX phases in lithium ion or other batteries.