Punskovsky, J. | Search bioRxiv

bioRxiv2026

Rapid reconstitution and kinase-controlled regulation of algal pyrenoid condensates in engineered Nicotiana benthamiana

The pyrenoid is an organelle found in nearly all algae that concentrates CO2 around Rubisco to enhance photosynthetic carbon fixation. Engineering a functional pyrenoid into C plants is a promising route to improve plant photosynthetic performance and yields. However, progress has been limited by the lack of a plant platform for rapidly testing candidate components. Here, we engineered N. benthamiana to make its chloroplast Rubisco holoenzyme compatible with C. reinhardtii pyrenoid proteins. Disruption of native N. benthamiana RBCS genes and complementation with the C. reinhardtii RBCS2 generated a Rubisco-recombinant background where transient expression of the Rubisco linker protein EPYC1 was sufficient to drive the formation of Rubisco-EPYC1 condensates. Co-expression with the algal pyrenoid kinase KEY1 shifted the multi-condensate state toward a single condensate per chloroplast by altering EPYC1 phosphorylation in planta, recapitulating C. reinhardtii pyrenoid regulation. Together, these results establish engineered N. benthamiana as a tractable platform for rapidly characterizing candidate pyrenoid proteins and provide a step toward reconstructing pyrenoid architecture and regulation in plants.

plant biology↗

bioRxiv2024

Mechanisms Of Meristem Maintenance By Maize Transcriptional Corepressors

The formation of the plant body proceeds in a sequential post-embryonic manner through the action of meristems. Tightly coordinated meristem regulation is required for development and reproductive success, eventually determining yield in crop species. In maize, the REL2 family of transcriptional corepressors includes four members, REL2, RELK1 (REL2-LIKE1), RELK2, and RELK3. In a screen for rel2 enhancers, we identified shorter double mutants with enlarged female inflorescence meristems (IMs) carrying mutations in RELK1. Expression and genetic analysis indicate that REL2 and RELK1 cooperatively regulate female IM development by controlling genes involved in redox balance, hormone homeostasis, and differentiation, ultimately tipping the meristem toward an environment favorable to expanded expression of the ZmWUSCHEL1 gene, a key stem-cell promoting transcription factor. We further demonstrate that RELK genes have partially redundant yet diverse functions in the maintenance of various meristem types during development. By exploiting subtle increases in ear IM size in rel2 heterozygous plants, we also show that extra rows of kernels are formed across a diverse set of F1 hybrids. Our findings reveal that the REL2 family maintains development from embryonic initiation to reproductive growth and can potentially be harnessed for increasing seed yield in a major crop species. One sentence summaryREL2-RELKs fine tune hormone and chemical cues to prevent expanded expression of ZmWUSCHEL1 in maize inflorescence meristems, and can potentially be harnessed for increasing seed yield in hybrids.

plant biology↗