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1. Parsing a plethora of pollen: the role of pollen size and shape in the evolution of Boraginaceae

   https://doi.org/10.1111/cla.12488  

   Noroozi, Maryam; Ghahremaninejad, Farrokh; Bogler, David; Witherspoon, Jocelyn M.; Ryan, Gillian L.; Miller, James S.; Riahi, Mehrshid; Cohen, James I. (August 2021, Cladistics)

   Abstract Pollen, the microgametophyte of seed plants, has an important role in plant reproduction and, therefore, evolution. Pollen is variable in, for example, size, shape, aperture number; these features are particularly diverse in some plant taxa and can be diagnostic. In one family, Boraginaceae, the range of pollen diversity suggests the potential utility of this family as a model for integrative studies of pollen development, evolution and molecular biology. In the present study, a comprehensive survey of the diversity and evolution of pollen from 538 species belonging to 72 genera was made using data from the literature and additional scanning electron microscopy examination. Shifts in diversification rates and the evolution of various quantitative characters were detected, and the results revealed remarkable differences in size, shape and number of apertures. The pollen of one subfamily, Boraginoideae, is larger than that in Cynoglossoideae. The diversity of pollen shapes and aperture numbers in one tribe, Lithospermeae, is greater than that in the other tribes. Ancestral pollen for the family was resolved as small, prolate grains that bear three apertures and are iso‐aperturate. Of all the tribes, the greatest number of changes in pollen size and aperture number were observed in Lithospermeae and Boragineae, and the number of apertures was found to be stable throughout all tribes of Cynoglossoideae. In addition, the present study showed that diversification of Boraginaceae cannot be assigned to a single factor, such as pollen size, and the increased rate of diversification for species‐rich groups (e.g.Cynoglossum) is not correlated with pollen size or shape evolution. The palynological data and patterns of character evolution presented in the study provide better resolution of the roles of geographical and ecological factors in the diversity and evolution of pollen grains of Boraginaceae, and provide suggestions for future palynological research across the family. 

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2. Building portals in pollen

   https://doi.org/10.1038/s41477-020-0641-3  

   Zhou, Yuan; Dobritsa, Anna A. (April 2020, Nature Plants)
3. Bioelectricity and the Control of Apical Growth in Pollen Tubes

   https://doi.org/10.1089/bioe.2023.0006  

   Oliveira Nunes, Custódio de; Feijó, José A. (March 2023, Bioelectricity)
4. Molecular mechanisms of pollen aperture formation in Arabidopsis and rice

   https://doi.org/10.1093/jxb/eraf397  

   Zhou, Yuan; Dobritsa, Anna_A; Melzer, ed., Rainer (September 2025, Journal of Experimental Botany)

   Abstract Apertures are specialized regions on the pollen surface that receive little to no exine deposition, forming distinct structures important for pollen function. Aperture number, shape, and positions vary widely across species, resulting in diverse, species-specific patterns that make apertures fascinating from both cell biological and evolutionary perspectives. Aperture formation requires developing pollen to establish polarity and define specific regions of the plasma membrane as aperture domains. In the decade or so since the discovery of the first aperture factor, INAPERTURATE POLLEN1 (INP1), pollen apertures have become a powerful model for investigating how cells form distinct plasma membrane domains. Recent studies in Arabidopsis and rice, two species with contrasting aperture patterns, have identified key molecular players that regulate aperture domain specification and development. In this review, we summarize these advances and discuss directions for future studies on the molecular mechanisms controlling aperture formation. 

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5. Characterization of novel pollen-expressed transcripts reveals their potential roles in pollen heat stress response in Arabidopsis thaliana

   https://doi.org/10.1007/s00497-020-00400-1  

   Rutley, Nicholas; Poidevin, Laetitia; Doniger, Tirza; Tillett, Richard L.; Rath, Abhishek; Forment, Javier; Luria, Gilad; Schlauch, Karen A.; Ferrando, Alejandro; Harper, Jeffery F.; et al (March 2021, Plant Reproduction)

   null (Ed.)

   Abstract Key message Arabidopsis pollen transcriptome analysis revealed new intergenic transcripts of unknown function, many of which are long non-coding RNAs, that may function in pollen-specific processes, including the heat stress response. Abstract The male gametophyte is the most heat sensitive of all plant tissues. In recent years, long noncoding RNAs (lncRNAs) have emerged as important components of cellular regulatory networks involved in most biological processes, including response to stress. While examining RNAseq datasets of developing and germinating Arabidopsis thaliana pollen exposed to heat stress (HS), we identified 66 novel and 246 recently annotated intergenic expressed loci (XLOCs) of unknown function, with the majority encoding lncRNAs. Comparison with HS in cauline leaves and other RNAseq experiments indicated that 74% of the 312 XLOCs are pollen-specific, and at least 42% are HS-responsive. Phylogenetic analysis revealed that 96% of the genes evolved recently in Brassicaceae . We found that 50 genes are putative targets of microRNAs and that 30% of the XLOCs contain small open reading frames (ORFs) with homology to protein sequences. Finally, RNAseq of ribosome-protected RNA fragments together with predictions of periodic footprint of the ribosome P-sites indicated that 23 of these ORFs are likely to be translated. Our findings indicate that many of the 312 unknown genes might be functional and play a significant role in pollen biology, including the HS response. 

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