Arabidopsis annexin 5 controls plasma membrane properties in mature pollen grains

In Arabidopsis, a dry stigma surface enables a gradual hydration of pollen grains by a controlled release of water. Occasionally the grains may be exposed to extreme precipitations that cause rapid water influx, swelling and eventually lead to pollen membrane (PM) rupture. In metazoans, calcium- and phospholipids-binding proteins, referred to as annexins participate in repair of the plasma membrane damages. It remains unclear, however, how this process is conducted in plants. Here, we examined whether the plant annexin 5 (ANN5), the most abundant member of the annexin family in pollen, is involved in the restoration of PM integrity. We analyzed a cellular dynamics of ANN5 in the pollen grains undergoing in vitro and in vivo hydration. We observed a transient ANN5 association to PM during the in vitro hydration that did not occur in the pollen grains being hydrated on the stigma. To simulate a rainfall, we performed spraying of the pollinated stigma with deionized water that induced ANN5 accumulation at PM. Similarly, calcium or magnesium application affected PM properties and induced ANN5 recruitment to PM. Our data suggest a model, in which ANN5 is involved in the maintenance of membrane integrity in pollen grains exposed to osmotic or ionic imbalances.

Expression of Brassica napus GLO1 is sufficient to breakdown artificial self-incompatibility in Arabidopsis thaliana

Members of the Brassicaceae family have the ability to regulate pollination events occurring on the stigma surface. In Brassica species, self-pollination leads to an allele specific interaction between the pollen small cysteine-rich peptide ligand (SCR/SP11) and the stigmatic S-receptor kinase (SRK) that activates the E3 ubiquitin ligase ARC1 (Armadillo repeat-containing 1), resulting in proteasomal degradation of various compatibility factors including Glyoxalase I (GLO1) which is necessary for successful pollination. Suppression of GLO1 was sufficient to reduce compatibility, and overexpression of GLO1 in self-incompatible Brassica napus stigmas resulted in partial breakdown of the self-incompatibility response. Here, we verified if BnGLO1 could function as a compatibility factor in the artificial self-incompatibility system of Arabidopsis thaliana expressing AlSCRb, AlSRKb and AlARC1 proteins from A. lyrata. Overexpression of BnGLO1 is sufficient to breakdown self-incompatibility response in A. thaliana stigmas, suggesting that GLO1 functions as an inter-species compatibility factor. Therefore, GLO1 has an indisputable role as a compatibility factor in the stigma in regulating pollen attachment and pollen tube growth. Lastly, this study demonstrates the usefulness of an artificial self-incompatibility system in A. thaliana for interspecific self-incompatibility studies.

Identification of a role for an E6-like 1 gene in early pollen-stigma interactions in Arabidopsis thaliana

In Arabidopsis, successful pollen-stigma interactions are dependent on rapid recognition of compatible pollen by the stigmatic papillae located on the surface of the pistil and the subsequent regulation of pollen hydration and germination, and followed by the growth of pollen tubes through the stigma surface. Here we have described the function of a novel gene, E6-like 1 (E6L1), that was identified through the analysis of transcriptome datasets, as one of highest-expressed genes in the stigma, and furthermore, its expression was largely restricted to the stigma and trichomes. The first E6 gene was initially identified as a highly-expressed gene during cotton fiber development, and related E6-like predicted proteins are found throughout the Angiosperms. To date, no orthologous genes have been assigned a biological function. Both the Arabidopsis E6L1 and cotton E6 proteins are predicted to be secreted, and this was confirmed using an E6L1:RFP fusion construct. To further investigate E6L1’s function, one T-DNA and two independent CRISPR-generated mutants were analyzed for compatible pollen-stigma interactions, and pollen hydration, pollen adhesion and seed set were mildly impaired for the e6l1 mutants. This work identifies E6L1 as a novel stigmatic factor that plays a role during the early post-pollination stages in Arabidopsis.Key MessageWe describe a function for a novel Arabidopsis gene, E6-like 1 (E6L1), that was identified as a highly-expressed gene in the stigma and plays a role in early post-pollination stages.

POLLEN ATAU SERBUK SARI : ASPEK MORFOLOGI, SISTEMATIKA DAN APLIKASINYA PADA TUMBUHAN KELUARGA MENTOL

Pollen Powder or Sari : Aspects of Morphology, Systematics and Application on Menthol Family Plant Pollen is the important component of plant to develop through reproductive. Pollen is the male organ of plants that plays an important role in the process of the evolution of plants. Menthol family plants (the Family Lamiaceae) is one of biggest families after Asteraceae. The process of the cross breeding often dominates the process of the evolution to the ment al Family. The research on the menthol Family's pollen aimed to know the affinity and the process of his pollination. The form of pollen of the Family Lamiaceae, was round and hexacolpate, the form was the same as the species member with their relatives. In the process of pollination often helped by the bee where pollen that clung to the abdomen part and the chest of the bee and moved to the other flower where the cross-pollination happen. The process of the cross-pollination happened also because of the same of maturity time between pollen of male and the stigma surface of female. The seed was still being the dominant factor in the reproductive in the Family Lamiaceae. Key words : Pollen, Pollination, Lamiaceae, the Mint family, the bee, the seed Abstrak Serbuk sari atau dikenal dengan pollen merupakan komponen penting tanaman untuk berkembang melalui reproduktif. Serbuk sari merupakan organ jantan pada tumbuhan yang berperan penting dalam proses evolusi tumbuhan. Tumbuhan Keluarga Mentol (Famili Lamiaceae) merupakan salah satu Famili yang terbesar setelah Asteraceae. Proses perkawinan silang banyak mendominasi proses evolusi pada Keluarga Mentol. Penelitian terhadap serbuk sari Keluarga Mentol bertujuan untuk mengetahui kekerabatan dan proses penyerbukannya. Bentuk morfologi serbuk sari pada Famili Lamiaceae, yaitu bulat dan heksakolpat (hexacolpate), bentuk yang sama dengan jenis – jenis anggota Famili Lamiaceae. Pada proses penyerbukan banyak dibantu oleh lebah dimana pollen yang menempel pada bagian perut dan dada lebah penyerbuk dan berpindah pada bunga yang lain sehingga terjadi penyerbukan silang. Proses penyerbukan silang terjadi juga karena adanya waktu pemasakan yang sama antara serbuk sari sebagai organ jantan dan kepala putik sebagai organ betina. Biji masih merupakan faktor yang dominan pada perbanyakan Famili Lamiaceae.Kata kunci : Serbuk sari, Pollen, Lamiaceae, Keluarga Mentol, Lebah, biji.

Significance of stigma receptivity in intergeneric cross-pollination of Salix × Populus

The pollen–stigma interaction plays an important role in reproductive process and has been continuously studied in many interspecific and intergeneric crossing experiments. The aim of this study was to investigate stigma receptivity (SR) of willow in order to determine the most suitable period for its pollination with poplar pollen and improve the effectiveness of <em>Salix × Populus</em> crosses. Tissue samples were examined histologically using light, epifluorescent, scanning, and transmission electron microscopy. Willow SR was determined by stigma morphological traits, test of pollen germination rate, Peroxtesmo test of peroxidase and esterase activity on stigma surface as well as papilla ultrastructure at anthesis. We have ascertained that the SR duration in willow is short, lasting from 1 to 2 DA. The poplar pollen germination rate on willow stigmas on 1 DA ranged from 26.3 to 11.2%.

The morphology of the stigma surface of Petunia hybrida hort. superbissima as seen in scanning electron microscopy

The ultrastructure of stigma surface in allotetraploid petunias was analyzed by scanning electron microscopy. The stigma forms a bilobed structure with. a distinct central depression. The stigma surface is covered with numerous. papillate hairs of ununiform sizes and shapes.

Stigma-pollen recognition: a new look

During the last two decades, there have been several conceptual developments in our understanding of pollen-stigma recognition and molecular mechanisms involved. The main models proposed are compared. Based on additional data a hypothesis to complete these models especially for pollen hydration and adhesion is proposed. After attachment of the pollen to the stigma surface a close interaction exists involving lipoproteic membrane-like compounds (pollenkitt and stigma pellicle) and pollen agglutinating ability.

Localization of Ca2+ and Ca-ATPase on wet (Ruscus aculeatus) and dry (Primula officinalis) stigma surface

Calcium is present in the surface cells of both types of stigma. The chlorotetracycline method was used to show that the papillae of the dry stigma of <i>Primula officinalis</i> are the source of fluorescence of the CTC-Ca²⁺ complex. The precipitation method (NHA) localized calcium ions mainly in the pellicula surrounding these papillae. The NHA-Ca²⁺ precipitates were localized on the plasma membrane in the papillae of the wet stigma of <i>Ruscus aculeatus</i>. Ca-ATPase activity was found in both types of stigma in sites where the presence of Ca²⁺ had been determined.

Pollination in the Antarctic flowering plant Colobanthus quitensis (Kunth) Bartl.

<i>Colobanthus quitensis</i> forms chasmogamic and cleistogamic flowers. Their structure signals the possibility of both cross-pollination and self-pollination. In favorable conditions (natural or laboratory), flowers open creating a possibility for cross-pollination. The occurrence of cleistogamy in the investigated species may be conditioned by abiotic factors: low temperature, high air humidity, and strong wind. In closed flowers, a part of pollen grains reaches the stigma surface, and the rest remains inside the microsporangium. Pollen grains germinate on the stigma surface or inside the microsporangium. Often, two or more pollen tubes grow from a single pollen grain. Closed flowers and the direct contact between the style stigma and anther prove the preference for autogamy. Autogamy ensures the reproductive success of the investigated plant in the exceptionally harsh Antarctic environment.

Structural features of Rhododendron luteum flower

The flower of Rhododendron luteum (L.) Sweet has a pentamerous structure with radial symmetry. The anthers filament surface is covered by dense non-glandular hairs to the half of the height. The tubular anther dehisces along creating two openings in the anther-sac walls and the viscous pollen is released through two splits along the anther lobes. The pistil is pentamerous and the axial channel is filled with a mucilaginous secretion product which is continuous with the exudate on the stigma surface. The stigmatic papillae are densely packed and their exudate is stained intensively red for carbohydrates, while pollen grains are stained positively for lipids. The five-locular ovary has isomerous carpels (syncarpous gynoecium) and the ovary surface is covered by numerous, densely-packed glandular and non-glandular hairs protecting the nectar against transpiration. Numerous ovules per locule occur with one integument and a thin-walled megasporiangium. In carpels, oil cells occur sporadically as solitary idioblasts, located around the vascular bundles. Transmitting tissue cells contain a large central, electron translucent vacuole, filling most of the cell containing dark osmiophilic bodies homogenous or granular in appearance.