AtVPS41-mediated endocytic pathway is essential for pollen tube–stigma interaction in Arabidopsis
Sunday, 2016/06/05 | 06:21:26
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Lihong Hao, Jingjing Liu, Sheng Zhong, Hongya Gu, and Li-Jia Qu SignificanceSignaling pathways responsive to both external and internal signals are essential for implementation of biological functions in a cell. After perceiving the signal, the signaling needs to be attenuated and terminated, usually mediated by the endocytic trafficking, to ensure a temporal and spatial control of the signaling activities. In mammals, disruption of the vacuolar protein sorting 41 (VPS41)-mediated endocytic pathway was reported to cause pleiotropic diseases such as neurological disorders. However, the role of the endocytic pathway in plant cells is unknown. We report here that a VPS41-mediated late stage of the endocytic pathway is essential for male–female interaction in Arabidopsis. AbstractIn flowering plants, extensive male–female interactions are required for successful fertilization in which various signaling cascades are involved. Prevacuolar compartments (PVC) and vacuoles are two types of subcellular compartments that terminate signal transduction by sequestrating signaling molecules in yeast and mammalian cells; however, the manner in which they might be involved in male–female interactions in plants is unknown. In this study, we identified Arabidopsis thaliana vacuolar protein sorting 41 (AtVPS41), encoded by a single-copy gene with sequence similarity to yeast Vps41p, as a new factor controlling pollen tube–stigma interaction. Loss of AtVPS41 function disrupted penetration of pollen tubes into the transmitting tissue and thus led to failed male transmission. In the pollen tubes, AtVPS41 protein is associated with PVCs and the tonoplast. We demonstrate that AtVPS41 is required for the late stage of the endocytic pathway (i.e., endomembrane trafficking from PVCs to vacuoles) because internalization of cell-surface molecules was normal in the vps41-deficient pollen tubes, whereas PVC-to-vacuole trafficking was impaired. We further show that the CHCR domain is required for subcellular localization and biological functioning of AtVPS41. These results indicate that the AtVPS41-mediated late stage of the endocytic pathway is essential for pollen tube–stigma interaction in Arabidopsis.
See: http://www.pnas.org/content/113/22/6307.full PNAS June 1 2016; vol.113; no.22: 6307–6312
Fig. 1. Phenotype characterization of vps41 pollen. (A) Diagram of T-DNA insertion sites in the two vps41 alleles. Green box, exons; black line, introns; blue box, untranslated regions. (B and C) vps41 pollen and vps41/gVPS41-GFP pollen germinated semi-in vivo after hand-limited pollination on the emasculated wild-type stigma. Compared with vps41/gVPS41-GFP–complemented pollen tubes, fewer vps41 pollen tubes penetrated the style. (D) Percentage of penetration of vps41 pollen tubes (n = 70) and vps41/gVPS41-GFP pollen tubes (n = 70) into the style 2.5 hag semi-in vivo. Error bars indicate SD; P value < 0.01. (E) Pollen tube length of vps41 pollen (n = 4) and vps41/gVPS41-GFP pollen (n = 29) 2.5 hag semi-in vivo. Error bars indicate SD; P value < 0.01. (F–I) Aniline blue staining assay of emasculated wild-type pistils pollinated with vps41/gVPS41-GFP pollen (F) and vps41 pollen (G–I) 48 h after pollination. (Scale bars: 100 μm in F and G; 50 μm in H and I.) (J) Bar graph of percentage of pollen tubes growing in the transmitting tract; for vps41/gVPS41-GFP pollen, n = 67, and four independent pistils were statistically analyzed; for vps41 pollen, n = 95; and six independent pistils were statistically analyzed. Error bars indicate SD; P value < 0.01. (K) Thirty days after pollination, while there were mature seeds in the siliques pollinated with vps41/gVPS41-GFP pollen (Right), no seed was seen in the siliques pollinated with vps41 pollen (Left). (Scale bar, 500 μm.). |
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