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Wang X, Li T, Xu J, Zhang F, Liu L, Wang T, Wang C, Ren H, Zhang Y. Distinct functions of microtubules and actin filaments in the transportation of the male germ unit in pollen. Nat Commun 2024; 15:5448. [PMID: 38937444 PMCID: PMC11211427 DOI: 10.1038/s41467-024-49323-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Accepted: 06/02/2024] [Indexed: 06/29/2024] Open
Abstract
Flowering plants rely on the polarized growth of pollen tubes to deliver sperm cells (SCs) to the embryo sac for double fertilization. In pollen, the vegetative nucleus (VN) and two SCs form the male germ unit (MGU). However, the mechanism underlying directional transportation of MGU is not well understood. In this study, we provide the first full picture of the dynamic interplay among microtubules, actin filaments, and MGU during pollen germination and tube growth. Depolymerization of microtubules and inhibition of kinesin activity result in an increased velocity and magnified amplitude of VN's forward and backward movement. Pharmacological washout experiments further suggest that microtubules participate in coordinating the directional movement of MGU. In contrast, suppression of the actomyosin system leads to a reduced velocity of VN mobility but without a moving pattern change. Moreover, detailed observation shows that the direction and velocity of VN's movement are in close correlations with those of the actomyosin-driven cytoplasmic streaming surrounding VN. Therefore, we propose that while actomyosin-based cytoplasmic streaming influences on the oscillational movement of MGU, microtubules and kinesins avoid MGU drifting with the cytoplasmic streaming and act as the major regulator for fine-tuning the proper positioning and directional migration of MGU in pollen.
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Affiliation(s)
- Xiangfei Wang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Tonghui Li
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Jiuting Xu
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Fanfan Zhang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Lifang Liu
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Ting Wang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Chun Wang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China
| | - Haiyun Ren
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China.
- Center for Biological Science and Technology, Guangdong Zhuhai-Macao Joint Biotech Laboratory, Beijing Normal University, 519087, Zhuhai, China.
| | - Yi Zhang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, 100875, Beijing, China.
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Del Casino C, Conti V, Licata S, Cai G, Cantore A, Ricci C, Cantara S. Mitigation of UV-B Radiation Stress in Tobacco Pollen by Expression of the Tardigrade Damage Suppressor Protein (Dsup). Cells 2024; 13:840. [PMID: 38786062 PMCID: PMC11119994 DOI: 10.3390/cells13100840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/19/2024] [Accepted: 04/23/2024] [Indexed: 05/25/2024] Open
Abstract
Pollen, the male gametophyte of seed plants, is extremely sensitive to UV light, which may prevent fertilization. As a result, strategies to improve plant resistance to solar ultraviolet (UV) radiation are required. The tardigrade damage suppressor protein (Dsup) is a putative DNA-binding protein that enables tardigrades to tolerate harsh environmental conditions, including UV radiation, and was therefore considered as a candidate for reducing the effects of UV exposure on pollen. Tobacco pollen was genetically engineered to express Dsup and then exposed to UV-B radiation to determine the effectiveness of the protein in increasing pollen resistance. To establish the preventive role of Dsup against UV-B stress, we carried out extensive investigations into pollen viability, germination rate, pollen tube length, male germ unit position, callose plug development, marker protein content, and antioxidant capacity. The results indicated that UV-B stress has a significant negative impact on both pollen grain and pollen tube growth. However, Dsup expression increased the antioxidant levels and reversed some of the UV-B-induced changes to pollen, restoring the proper distance between the tip and the last callose plug formed, as well as pollen tube length, tubulin, and HSP70 levels. Therefore, the expression of heterologous Dsup in pollen may provide the plant male gametophyte with enhanced responses to UV-B stress and protection against harmful environmental radiation.
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Affiliation(s)
- Cecilia Del Casino
- Dipartimento di Scienze della Vita, University of Siena, via Mattioli 4, 53100 Siena, Italy; (C.D.C.); (S.L.)
| | - Veronica Conti
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, via Irnerio 42, 40126 Bologna, Italy;
| | - Silvia Licata
- Dipartimento di Scienze della Vita, University of Siena, via Mattioli 4, 53100 Siena, Italy; (C.D.C.); (S.L.)
| | - Giampiero Cai
- Dipartimento di Scienze della Vita, University of Siena, via Mattioli 4, 53100 Siena, Italy; (C.D.C.); (S.L.)
| | - Anna Cantore
- Department of Medical, Surgical and Neurological Sciences, University of Siena, Viale Bracci, 53100 Siena, Italy; (A.C.); (C.R.); (S.C.)
| | - Claudia Ricci
- Department of Medical, Surgical and Neurological Sciences, University of Siena, Viale Bracci, 53100 Siena, Italy; (A.C.); (C.R.); (S.C.)
| | - Silvia Cantara
- Department of Medical, Surgical and Neurological Sciences, University of Siena, Viale Bracci, 53100 Siena, Italy; (A.C.); (C.R.); (S.C.)
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Sugi N, Izumi R, Tomomi S, Susaki D, Kinoshita T, Maruyama D. Removal of the endoplasma membrane upon sperm cell activation after pollen tube discharge. FRONTIERS IN PLANT SCIENCE 2023; 14:1116289. [PMID: 36778680 PMCID: PMC9909283 DOI: 10.3389/fpls.2023.1116289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
In pollen and pollen tubes, immotile sperm cells are enclosed by an inner vegetative plasma membrane (IVPM), a single endomembrane originating from the vegetative-cell plasma membrane. It is widely believed that sperm cells must be removed from the IVPM prior to gamete associations and fusions; however, details of the timing and morphological changes upon IVPM dissociation remain elusive. Here, we report a rapid IVPM breakdown immediately before double fertilization in Arabidopsis thaliana. The IVPM was stably observed in coiling pollen tubes when pollen tube discharge was prevented using lorelei mutant ovules. In contrast, a semi-in vivo fertilization assay in wild-type ovules demonstrated fragmented IVPM around sperm nuclei 1 min after pollen tube discharge. These observations revealed the dynamic alteration of released sperm cells and provided new insights into double fertilization in flowering plants. With a summary of recent findings on IVPM lipid composition, we discussed the possible physiological signals controlling IVPM breakdown.
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Pasten MC, Carballo J, Gallardo J, Zappacosta D, Selva JP, Rodrigo JM, Echenique V, Garbus I. A combined transcriptome - miRNAome approach revealed that a kinesin gene is differentially targeted by a novel miRNA in an apomictic genotype of Eragrostis curvula. FRONTIERS IN PLANT SCIENCE 2022; 13:1012682. [PMID: 36247597 PMCID: PMC9563718 DOI: 10.3389/fpls.2022.1012682] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 09/14/2022] [Indexed: 06/06/2023]
Abstract
Weeping lovegrass (Eragrostis curvula [Shrad.] Nees) is a perennial grass typically established in semi-arid regions, with good adaptability to dry conditions and sandy soils. This polymorphic complex includes both sexual and apomictic cytotypes, with different ploidy levels (2x-8x). Diploids are known to be sexual, while most polyploids are facultative apomicts, and full apomicts have also been reported. Plant breeding studies throughout the years have focused on achieving the introgression of apomixis into species of agricultural relevance, but, given the complexity of the trait, a deeper understanding of the molecular basis of regulatory mechanisms of apomixis is still required. Apomixis is thought to be associated with silencing or disruption of the sexual pathway, and studies have shown it is influenced by epigenetic mechanisms. In a previous study, we explored the role of miRNA-mRNA interactions using two contrasting E. curvula phenotypes. Here, the sexual OTA-S, the facultative Don Walter and the obligate apomictic Tanganyika cDNA and sRNA libraries were inquired, searching for miRNA discovery and miRNA expression regulation of genes related to the reproductive mode. This allowed for the characterization of seven miRNAs and the validation of their miRNA-target interactions. Interestingly, a kinesin gene was found to be repressed in the apomictic cultivar Tanganyika, targeted by a novel miRNA that was found to be overexpressed in this genotype, suggestive of an involvement in the reproductive mode expression. Our work provided additional evidence of the contribution of the epigenetic regulation of the apomictic pathway.
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Affiliation(s)
- María Cielo Pasten
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
| | - José Carballo
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
| | - Jimena Gallardo
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
- Departamento de Agronomía, Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
| | - Diego Zappacosta
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
- Departamento de Agronomía, Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
| | - Juan Pablo Selva
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
| | - Juan Manuel Rodrigo
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
- Departamento de Agronomía, Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
| | - Viviana Echenique
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
- Departamento de Agronomía, Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
| | - Ingrid Garbus
- Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina
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Cai G. The legacy of kinesins in the pollen tube thirty years later. Cytoskeleton (Hoboken) 2022; 79:8-19. [PMID: 35766009 PMCID: PMC9542081 DOI: 10.1002/cm.21713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 06/06/2022] [Accepted: 06/27/2022] [Indexed: 11/10/2022]
Abstract
The pollen tube is fundamental in the reproduction of seed plants. Particularly in angiosperms, we now have much information about how it grows, how it senses extracellular signals, and how it converts them into a directional growth mechanism. The expansion of the pollen tube is also related to dynamic cytoplasmic processes based on the cytoskeleton (such as polymerization/depolymerization of microtubules and actin filaments) or motor activity along with the two cytoskeletal systems and is dependent on motor proteins. While a considerable amount of information is available for the actomyosin system in the pollen tube, the role of microtubules in the transport of organelles or macromolecular structures is still quite uncertain despite that 30 years ago the first work on the presence of kinesins in the pollen tube was published. Since then, progress has been made in elucidating the role of kinesins in plant cells. However, their role within the pollen tube is still enigmatic. In this review, I will postulate some roles of kinesins in the pollen tube 30 years after their initial discovery based on information obtained in other plant cells in the meantime. The most concrete hypotheses predict that kinesins in the pollen tube enable the short movement of specific organelles or contribute to generative cell or sperm cell transport, as well as mediate specific steps in the process of endocytosis.
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Affiliation(s)
- Giampiero Cai
- Dipartimento Scienze della Vita, Università di Siena, via Mattioli 4, Siena, Italy
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