Plant Gene and Trait 2025, Vol.16, No.3, 123-132 http://genbreedpublisher.com/index.php/pgt 124 2.2 Pollination mechanisms in cucumbers The pollination of cucumbers is mainly accomplished by bees and wild bees (Lowenstein et al., 2015). They carry pollen from the male flowers to the stigma of the female flowers. Then the pollen begins to germinate, the pollen tube grows downward, and finally fertilization is completed. The quantity and vitality of pollen, as well as the fertilization ability of the stigma, are the keys to successful pollination (Kaur et al., 2021). At the molecular level, some enzymes, such as CsCWIN3, can regulate sugar supply and have an impact on pollen development, pollen tube growth and seed formation (Figure 1) (Fan et al., 2024). Moreover, soil nutrients can affect the quantity and composition of pollen and nectar, thereby influencing the number of visits by pollinators and the pollination effect (Li et al., 2021; Patch et al., 2022). Figure 1 Expression of CsCWIN3 and localization of its protein in pollinated stigma and fertilized ovules in WT cucumber (Adopted from Fan et al., 2024) Image caption: A to F) In situ hybridization of CsCWIN3 in pollinated stigma and fertilized ovule. CsCWIN3 was expressed in PG, PT, Pp, VB, TT, PlVB, Fu, and Ov A, C, E). Asterisks indicate positive signal. B, D, F) Negative control for in situ hybridization using CsCWIN3 sense probe in the pollinated stigma B), style D), and the fertilized ovary/ovule F). G to L) Fluorescence immunolocalization of CsCWIN3 protein in pollinated stigma and fertilized ovule. CsCWIN3 was located in PG, PT, Pp, VB, TT, PlVB, Fu, and Ov. Asterisks highlight the protein signals. The secondary antibody was fluorescein isothiocyanate (FITC)-labeled anti-rabbit IgG. The green color indicates fluorescence from FITC. G, I, K) Green fluorescence-field image in the pollinated stigma G), style I), and the fertilized ovary/ovule K), respectively. H, J, L) Merged images of green fluorescence- and bright-field in the pollinated stigma H), style J), and the fertilized ovary/ovule L), respectively. The boxed insets in A), C), and G) were the close-up images, showing the signals in the germinated PGA, G) and the pollinated TT tissue C). Scale bars: 200 μm. Fu, funiculus; Ov,ovule; PG, pollen grain; PlVB, placenta vascular bundle; Pp, papillae cell; PT, pollen tube; TT, transmitting tract; VB, vascular bundle (Adopted from Fan et al., 2024)
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