Minghao Qu

Shoot branching affects plant architecture. In strawberry (Fragaria L.), short branches (crowns) develop from dormant axillary buds to form inflorescences and flowers. While this developmental transition contributes greatly to perenniality and yield in strawberry, its regulatory mechanism remains unclear and understudied. In the woodland strawberry (Fragaria vesca), we identified and characterized two independent mutants showing more crowns. Both mutant alleles reside in FveMYB117a, a R2R3-MYB transcription factor gene highly expressed in shoot apical meristems, axillary buds and young leaves. Transcriptome analysis revealed that the expression of several cytokinin pathway genes was altered in the fvemyb117a mutant. Consistently, active cytokinins were significantly increased in the axillary buds of the fvemyb117a mutant. Exogenous application of cytokinin enhanced crown outgrowth in the wild type, whereas the cytokinin inhibitors suppressed crown outgrowth in the fvemyb117a mutant. FveMYB117a binds directly to the promoters of the cytokinin homeostasis genes FveIPT2 encoding an isopentenyltransferase and FveCKX1 encoding a cytokinin oxidase to regulate their expression. Conversely, the type-B Arabidopsis response regulators FveARR1 and FveARR2b can directly inhibit the expression of FveMYB117a, indicative of a negative feedback regulation. In conclusion, we identified FveMYB117a as a key repressor of crown outgrowth by inhibiting cytokinin accumulation and provide a mechanistic basis for bud fate transition in an herbaceous perennial plant.

Water chestnut (Trapa L.) is a floating-leaved aquatic plant with high edible and medicinal value. In this study, we presented chromosome-level genome assemblies of cultivated large-seed species Trapa bicornis and its wild small-seed relative Trapa incisa by using PacBio HiFi long reads and Hi-C technology. The T. bicornis and T. incisa assemblies consisted of 479.90 Mb and 463.97 Mb contigs with N50 values of 13.52 Mb and 13.77 Mb, respectively, and repeat contents of 62.88% and 62.49%, respectively. A total of 33,306 and 33,315 protein-coding genes were predicted in T. bicornis and T. incisa assemblies, respectively. There were 159,232 structural variants affecting more than 11 thousand genes detected between the two genomes. The phylogenetic analysis indicated that the lineage leading to Trapa was diverged from the lineage to Sonneratia approximately 23 million years ago. These two assemblies provide valuable resources for future evolutionary and functional genomic research and molecular breeding of water chestnut.

As the cornerstone of photovoltaitics industry, silicon solar cell draws extensive interests and its progress on conversion efficiency concerns the implementation of carbon neutrality promise. In order to achieve high efficiency, good surface passivation, low contact resistance and transparent front skin are the indispensable requirements, bringing about variety of technologies and strategies to balance out for maximum efficiency. Recently, our group achieved a new world record, 26.81%, in silicon solar cells using improved heterojunction technology (SHJ). Thanks to the successful integration of nanocrystalline doped hydrogenated silicon (nc-Si:H), surface passivation quality is further enhanced by field effect and the contact resistance is highly restrained. On the other hand, oxygen doping at front nc-Si:H broadens the band gap and the transparency to short-wavelength sunlight is increased for higher short-circuit current density. Combined with new transparent conductive oxide and advanced metallization, intrinsic properties of silicon emerge from intricate power loss mechanism, causing unprecedented fill factor and record conversion efficiency in silicon solar cells. Moreover, our record solar cell is based on front and rear contacted architecture with full-size commercial Czochralski silicon wafer and total-area certification. With the simplicity and compatibility of our SHJ technology to mass production, it is easy to transfer the result into industrial manufacture with high mass production cell conversion efficiency.

The development of high efficiency Si solar cells is seeing successful industrialization of carrier-selective and passivating contact technologies, including Tunnel Oxide Passivated Contact (TOPCon) and Silicon Heterojunction Technology (SHJ). Driven by cell technology innovation, the Si PV industry is making bold moves to see 26-27% efficiencies in mass production in the coming years. Undisputablly, Si wafer development provides strong support for the fast-upgrading cell technologies, and guarantees the technologies' deployment at affordable costs. To date, p-type Si wafer is dominating the market by 95% market share. However, a 5% to 50% uptaking of n-type Si wafer is predicted by ITRPV. One critical factor for this judgement is that the n-type Si solar cell efficiencies are leading ahead that of the p-type. It is well argued that the n-type Si wafer manufacturing can steadily ramp up given the demand, and the cost disadvantage can be alleviated to some extent with scaled production capacity. At the same time, the industry shall not ignore the inherent cost advantage of p-type wafers, and keep exploiting the possibilities to push up the p-type Si solar cell efficiency. In this work, we demonstrate that the p-type SHJ solar cell efficiency can reach 26.6%, which is just 0.2% behind of its n-type counterpart. This result establishes a solid foundation for further SHJ technology development on a cost-effective basis.