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1. The SvFUL2 transcription factor is required for inflorescence determinacy and timely flowering in Setaria viridis

   https://doi.org/10.1093/plphys/kiab169  

   Yang, Jiani ; Bertolini, Edoardo ; Braud, Max ; Preciado, Jesus ; Chepote, Adriana ; Jiang, Hui ; Eveland, Andrea L ( April 2021 , Plant Physiology)

   null (Ed.)

   Abstract Inflorescence architecture in cereal crops directly impacts yield potential through regulation of seed number and harvesting ability. Extensive architectural diversity found in inflorescences of grass species is due to spatial and temporal activity and determinacy of meristems, which control the number and arrangement of branches and flowers, and underlie plasticity. Timing of the floral transition is also intimately associated with inflorescence development and architecture, yet little is known about the intersecting pathways and how they are rewired during development. Here, we show that a single mutation in a gene encoding an AP1/FUL-like MADS-box transcription factor significantly delays flowering time and disrupts multiple levels of meristem determinacy in panicles of the C4 model panicoid grass, Setaria viridis. Previous reports of AP1/FUL-like genes in cereals have revealed extensive functional redundancy, and in panicoid grasses, no associated inflorescence phenotypes have been described. In S. viridis, perturbation of SvFul2, both through chemical mutagenesis and gene editing, converted a normally determinate inflorescence habit to an indeterminate one, and also repressed determinacy in axillary branch and floral meristems. Our analysis of gene networks connected to disruption of SvFul2 identified regulatory hubs at the intersection of floral transition and inflorescence determinacy, providing insights into the optimization of cereal crop architecture. 

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2. Exploring Grass Morphology & Mutant Phenotypes Using Setaria viridis

   https://doi.org/10.1525/abt.2021.83.5.311  

   Kaggwa, Ruth J. ; Jiang, Hui ; Ryan, Rita A. ; Zahller, Justin Paul ; Kellogg, Elizabeth A. ; Woodford-Thomas, Terry ; Callis-Duehl, Kristine ( May 2021 , The American Biology Teacher)

   null (Ed.)

   Globally, most human caloric intake is from crops that belong to the grass family (Poaceae), including sugarcane (Saccharum spp.), rice (Oryza sativa), maize (or corn, Zea mays), and wheat (Triticum aestivum). The grasses have a unique morphology and inflorescence architecture, and some have also evolved an uncommon photosynthesis pathway that confers drought and heat tolerance, the C4 pathway. Most secondary-level students are unaware of the global value of these crops and are unfamiliar with plant science fundamentals such as grass architecture and the genetic concepts of genotype and phenotype. Green foxtail millet (Setaria viridis) is a model organism for C4 plants and a close relative of globally important grasses, including sugarcane. It is ideal for teaching about grass morphology, the economic value of grasses, and the C4 photosynthetic pathway. This article details a teaching module that uses S. viridis to engage entire classrooms of students in authentic research through a laboratory investigation of grass morphology, growth cycle, and genetics. This module includes protocols and assignments to guide students through the process of growing one generation of S. viridis mutants and reference wild-type plants from seed to seed, taking measurements, making critical observations of mutant phenotypes, and discussing their physiological implications. 

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3. CFM1, a member of the CRM‐domain protein family, functions in chloroplast group II intron splicing in Setaria viridis

   https://doi.org/10.1111/tpj.15060  

   Feiz, Leila ; Asakura, Yukari ; Mao, Linyong ; Strickler, Susan R. ; Fei, Zhangjun ; Rojas, Margarita ; Barkan, Alice ; Stern, David B. ( December 2020 , The Plant Journal)

   The chloroplast RNA splicing and ribosome maturation (CRM) domain is a RNA‐binding domain found in a plant‐specific protein family whose characterized members play essential roles in splicing group I and group II introns in mitochondria and chloroplasts. Together, these proteins are required for splicing of the majority of the approximately 20 chloroplast introns in land plants. Here, we provide evidence fromSetaria viridisand maize that an uncharacterized member of this family, CRM Family Member1 (CFM1), promotes the splicing of most of the introns that had not previously been shown to require a CRM domain protein. ASetariamutant expressing mutated CFM1 was strongly disrupted in the splicing of three chloroplast tRNAs:trnI,trnVandtrnA. Analyses by RNA gel blot and polysome association suggest that the tRNA deficiencies lead to compromised chloroplast protein synthesis and the observed whole‐plant chlorotic phenotypes. Co‐immunoprecipitation data demonstrate that the maize CFM1 ortholog is bound to introns whose splicing is disrupted in thecfm1mutant. With these results, CRM domain proteins have been shown to promote the splicing of all but two of the introns found in angiosperm chloroplast genomes.

    

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4. Maize ANT1 modulates vascular development, chloroplast development, photosynthesis, and plant growth

   https://doi.org/10.1073/pnas.2012245117  

   Liu, Wen-Yu ; Lin, Hsin-Hung ; Yu, Chun-Ping ; Chang, Chao-Kang ; Chen, Hsiang-June ; Lin, Jinn-Jy ; Lu, Mei-Yeh Jade ; Tu, Shih-Long ; Shiu, Shin-Han ; Wu, Shu-Hsing ; et al ( September 2020 , Proceedings of the National Academy of Sciences)

   null (Ed.)

   Arabidopsis AINTEGUMENTA (ANT), an AP2 transcription factor, is known to control plant growth and floral organogenesis. In this study, our transcriptome analysis and in situ hybridization assays of maize embryonic leaves suggested that maize ANT1 (ZmANT1) regulates vascular development. To better understand ANT1 functions, we determined the binding motif of ZmANT1 and then showed that ZmANT1 binds the promoters of millet SCR1 , GNC , and AN3 , which are key regulators of Kranz anatomy, chloroplast development, and plant growth, respectively. We generated a mutant with a single-codon deletion and two frameshift mutants of the ANT1 ortholog in the C4 millet Setaria viridis by the CRISPR/Cas9 technique. The two frameshift mutants displayed reduced photosynthesis efficiency and growth rate, smaller leaves, and lower grain yields than wild-type (WT) plants. Moreover, their leaves sporadically exhibited distorted Kranz anatomy and vein spacing. Conducting transcriptomic analysis of developing leaves in the WT and the three mutants we identified differentially expressed genes (DEGs) in the two frameshift mutant lines and found many down-regulated DEGs enriched in photosynthesis, heme, tetrapyrrole binding, and antioxidant activity. In addition, we predicted many target genes of ZmANT1 and chose 13 of them to confirm binding of ZmANT1 to their promoters. Based on the above observations, we proposed a model for ANT1 regulation of cell proliferation and leaf growth, vascular and vein development, chloroplast development, and photosynthesis through its target genes. Our study revealed biological roles of ANT1 in several developmental processes beyond its known roles in plant growth and floral organogenesis. 

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5. Reproductive challenges related to a complex sexual system in Euphorbia rosescens , a rare endemic herb

   https://doi.org/10.1111/1442-1984.12409  

   Faivre, Amy E. ; Smith, Stacy A. ( April 2023 , Plant Species Biology)

   When the sexual system of a rare plant species is complex, characterizing floral development, plant morphology, and subpopulation structure is essential for assessing reproductive potential. Availability of pollinator rewards and positioning of sexual morphs within inflorescences relates to outcrossing potential. We studied the complex sexual system of the recently discoveredEuphorbia rosescensE.L. Bridges & Orzell, a rare species occurring in a single Florida county.Euphorbia rosescenshas both monomorphic subpopulations of female plants and mixed subpopulations with male and andromonoecious plants. Most data on cyathia sex, inflorescence architecture, floral visitors, and fruit set came from one female subpopulation and one mixed subpopulation. Cyathia longevity, flowering phase, nectar secretion, pollen production, and viability were measured in female, male, and hermaphrodite cyathia. Female plants had fewer inflorescence levels and cyathia and significantly smaller cyathia than male and andromonoecious plants. Andromonoecious plants were larger and produced more cyathia relative to male plants. Within mixed populations, sex switching occurred in both directions between male and andromonoecious plants. Female plants did not switch sexes. Proximal to distal inflorescence levels transitioned from hermaphrodite to male cyathia on andromonoecious plants. Nectar secretion corresponded to initiation of staminate flowering, but in female cyathia stigmas were receptive approximately a day before nectar secretion. Pollen production and viability were similar in male and hermaphrodite cyathia. Fruit maturation was minimal, primarily observed on andromonoecious plants. Nectar availability, pollen rewards, trimorphic inequalities in inflorescence display, and low fruit set suggest high geitonogamy, thus limiting outcrossing potential for this species.

    

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