Functional Pollen Research Articles

Temporal Petal Closure Benefits Reproductive Development of Magnolia denudata (Magnoliaceae) in Early Spring.

The Magnoliaceae shows strong phylogenetic niche conservatism, in which temporal petal closure has been extensively reported. However, it is yet elusive whether temporal petal closure is an idle floral character inherited from their ancestors or an adaptive trait to their habitats. Here, we monitored the process of temporal floral closure and re-opening in a thermogenic plant, Magnolia denudata (Magnoliaceae). Furthermore, we artificially interrupted temporal petal closure and investigated its effects on development of female and male gametophytes. Intriguingly, we found considerable anatomical changes in the anthers shortly after temporal closure of petals: disintegration of tapeta, crack of anther walls, and release of matured pollens. In comparison with normal flowers, artificially interrupted flowers (no petal closure) showed delayed anther development and slower pollen germination on stigmas, while little difference in embryo morphology was observed during the early stage of embryo development. Moreover, seed set and quality were significantly decreased when petal closure was prevented. In addition, we found pollination accelerated floral closure in M. denudata. Taken together, temporal floral closure benefits reproduction of M. denudata in early spring by promoting anther development and pollen function, which suggests that it is an adaptive floral trait to its specific habitat.

تأثیر نانو اکسید روی و شوری خاک بر میزان مشارکت ذخایر ساقه در عملکرد دانه، سرعت ظهور برگ و برخی شاخص های رشدی جو (Hordeum vulgaris L.)

Introduction Salinity is one of the major abiotic environmental stresses, which affect almost every aspect of plant life and significantly reduces crop yield. Thus it is a serious threat to agricultural productivity especially in arid and semi-arid regions. The response of plants to salinity depends on several factors such as developmental stage, severity, duration of stress, and cultivar genetics. Several strategies have been developed in order to decrease the toxic effects caused by high salinity on plant growth. Among them use of microelements such as zinc plays a very important role in yield improvement. Zinc is an essential micronutrient for humans, animals and plants, which act as the metal component of enzymes or as a functional structural. A number of researchers have reported the essentiality role of zinc for plant growth and yield. Zinc is required for chlorophyll production, pollen function, fertilization and germination plays an important role. So, recent researches have shown that a small amount of nutrients, particularly Zn applied by foliar spraying can affect the susceptibility of plants to stress. Zinc (Zn) is known as an important micronutrient and its deficiency is recognized as a critical problem in plants, especially grown on saline conditions with high pH values. Materials and methods In order to study of effects of foliar application with Nano zinc oxide on contribution of stem reserves in grain yield, leaf appearance rate and some growth indices of barley (Hordeum vulgaris L.) in various levels of soil salinity, a factorial experiment based on randomized complete block design with three replications was conducted at research greenhouse of faculty of Agriculture, University of Mohaghegh Ardabili in 2012. Experimental factors were included soil salinity in four levels (no salinity, salinity of 25, 50 and 75 Mm) with NaCl and foliar application of Nano-Zinc oxide at four levels (0 as control,0.25, 0.5, 0.75 and 1 g/lit). Results The results showed that increasing of soil salinity decreased yield, leaf appearance rate and growth indices of barley. It was vise versa in foliar application of Nano-Zinc oxide. Maximum of dry matter remobilization from stem and aerial vegetative organs was obtained in salinity of 75 Mm× no foliar application of Nano-Zinc. Means comparison showed that maximum of yield (1.22 g per plant), leaf appearance rate (0.466 leaf/ day) and growth indices were obtained in 0.75 g/lit of Nano-Zinc oxide× without of salinity application and minimum of they were obtained in no foliar application× soil salinity of 75 Mm. It seems that in order to increasing of yield and some growth indices such as total dry matter, crop growth rate and relative growth rate under salinity condition, can be suggested that be applied 0.75 g/lit of Nano-Zinc oxide.

The Tension-sensitive Ion Transport Activity of MSL8 is Critical for its Function in Pollen Hydration and Germination.

All cells respond to osmotic challenges, including those imposed during normal growth and development. Mechanosensitive (MS) ion channels provide a conserved mechanism for regulating osmotic forces by conducting ions in response to increased membrane tension. We previously demonstrated that the MS ion channel MscS-Like 8 (MSL8) is required for pollen to survive multiple osmotic challenges that occur during the normal process of fertilization, and that it can inhibit pollen germination. However, it remained unclear whether these physiological functions required ion flux through a mechanically gated channel provided by MSL8. We introduced two point mutations into the predicted pore-lining domain of MSL8 that disrupted normal channel function in different ways. The Ile711Ser mutation increased the tension threshold of the MSL8 channel while leaving conductance unchanged, and the Phe720Leu mutation severely disrupted the MSL8 channel. Both of these mutations impaired the ability of MSL8 to preserve pollen viability during hydration and to maintain the integrity of the pollen tube when expressed at endogenous levels. When overexpressed in an msl8-4 null background, MSL8I711S could partially rescue loss-of-function phenotypes, while MSL8F720L could not. When overexpressed in the wild-type Ler background, MSL8I711S suppressed pollen germination, similar to wild-type MSL8. In contrast, MSL8F720L failed to suppress pollen germination and increased pollen bursting, thereby phenocopying the msl8-4 mutant. Thus, an intact MSL8 channel is required for normal pollen function during hydration and germination. These data establish MSL8 as the first plant MS channel to fulfill previously established criteria for assignment as a mechanotransducer.

Application of Single Nucleotide Polymorphism Markers for Selection of Male Sterility in Crop Plants

Male sterility is an important trait and plays a key role for hybrid crop production in agricultural industry field. Different genes and enzymes are involved with male sterile traits. Dysfunction of these genes in any stage of male reproductive system often results in male sterility i.e., the inability to produce functional pollen. Functional male sterility can be utilized in the production of hybrid seed. During plant breeding for hybrid crop production, a lot of genetic diversities are created. Plant breeding is enhanced by the availability of molecular markers for rapid screening and selection in populations. Molecular markers are useful for a variety of purposes relevant to crop improvement. Functional markers that detect the functional mutations causing phenotypic changes offer a precise method for genetic identification. Various DNA markers are available now in plant breeding sectors. Among all of these markers, the new generation molecular markers called single nucleotide polymorphisms (SNPs) are most abundant, robust and feasible because of its availability in whole genome and that they play a key role in the induction of phenotypic variations like male sterility. In this review, we described the classification and mechanism of male sterility in crops, the genes responsible for male sterility, and application of SNP markers for selection of male sterile plants.

Experimental insights on the function of ancillary pollen and stigma polymorphisms in plants with heteromorphic incompatibility.

Most heterostylous plants possess a reciprocal arrangement of stigmas and anthers (reciprocal herkogamy), heteromorphic self-incompatibility, and ancillary polymorphisms of pollen and stigmas. The topographical complementarity hypothesis proposes that ancillary polymorphisms function in the rejection of incompatible pollen thus promoting disassortative pollination. Here, we test this hypothesis by investigating patterns of pollen transfer and capture in populations of dimorphic Armeria maritima and A. pubigera and distylous Limonium vulgare (Plumbaginaceae), and by studying pollen adherence and germination patterns in A. maritima following controlled hand-pollinations. Armeria lacks reciprocal herkogamy allowing the evaluation of the extent to which ancillary polymorphisms affect the composition of pollen loads. We compared the amounts of compatible and incompatible pollen on stigmas in natural populations and calculated the proficiencies of pollen transfer for each mating type. We detected disassortative pollination in each species, and mating types did not differ in compatible pollen capture, although cob stigmas captured more incompatible pollen. Controlled hand-pollinations revealed the failure of incompatible pollen to adhere and germinate on stigmas. Our results provided evidence that, while structural in nature, pollen-stigma dimorphisms are tightly associated with heteromorphic incompatibility and likely function to promote disassortative pollination, especially in the absence of reciprocal herkogamy.

Anatomy and Pollination of Cleistogamous Flowers of Benghal Dayflower (Commelina benghalensis)

The anatomy and pollination of subterranean cleistogamous flowers of Benghal dayflower (Commelina benghalensis) is described as a contribution to understanding its reproductive biology. Subterranean stems bear one spathe per node, each enclosing a single cleistogamous flower. Only the three anterior stamens produce functional pollen; the posterior three stamens are staminodes. Tapetum is amoeboid and endothecium is present. The three-carpellate superior ovary bears five dimorphic orthotropous ovules. Nearly mature flowers have straight to somewhat curved styles; at maturity, styles elongate and coil. Our observations indicate that coiled style growth causes rupture of anthers and brings pollen into contact with stigmas. Pollen tubes were observed in styles that had previously undergone coiling, located within mucilaginous secretions of the mature stylar canal. The subterranean cleistogamous flowers of Benghal dayflower and their apparently unique mode of pollination, viewed together with reproductive capacity of its aerial chasmogamous flowers, underscore the complexity and flexibility of the reproductive biology of this noxious weed species.

Biochemical characteristics of AtFAR2, a fatty acid reductase from Arabidopsis thaliana that reduces fatty acyl-CoA and -ACP substrates into fatty alcohols.

Fatty alcohols and derivatives are important for proper deposition of a functional pollen wall. Mutations in specific genes encoding fatty acid reductases (FAR) responsible for fatty alcohol production cause abnormal development of pollen. A disrupted AtFAR2 (MS2) gene in Arabidopsis thaliana results in pollen developing an abnormal exine layer and a reduced fertility phenotype. AtFAR2 has been shown to be targeted to chloroplasts and in a purified form to be specific for acyl-ACP substrates. Here, we present data on the in vitro and in planta characterizations of AtFAR2 from A. thaliana and show that this enzyme has the ability to use both, C16:0-ACP and C16:0-CoA, as substrates to produce C16:0-alcohol. Our results further show that AtFAR2 is highly similar in properties and substrate specificity to AtFAR6 for which in vitro data has been published, and which is also a chloroplast localized enzyme. This suggests that although AtFAR2 is the major enzyme responsible for exine layer functionality, AtFAR6 might provide functional redundancy to AtFAR2.

Pollen proteomics: from stress physiology to developmental priming.

Key messagePollen development and stress.In angiosperms, pollen or pollen grain (male gametophyte) is a highly reduced two- or three-cell structure which plays a decisive role in plant reproduction. Male gametophyte development takes place in anther locules where diploid sporophytic cells undergo meiotic division followed by two consecutive mitotic processes. A desiccated and metabolically quiescent form of mature pollen is released from the anther which lands on the stigma. Pollen tube growth takes place followed by double fertilization. Apart from its importance in sexual reproduction, pollen is also an interesting model system which integrates fundamental cellular processes like cell division, differentiation, fate determination, polar establishment, cell to cell recognition and communication. Recently, pollen functionality has been studied by multidisciplinary approaches which also include OMICS analyses like transcriptomics, proteomics and metabolomics. Here, we review recent advances in proteomics of pollen development and propose the process of developmental priming playing a key role to guard highly sensitive developmental processes.

Fuel for the road--sugar transport and pollen tube growth.

Pollen tubes require the activity of carbohydrate uptake transporters to sustain their high growth rate. The work of Rottmann and colleagues in this issue (pages 2387–2399) provides evidence that expression of a hexose transporter in pollen tubes may be regulated via the hexokinase signaling pathway. Pollen, the male gametophyte (haploid generation) of flowering plants, is responsible for delivering sperm cells to the egg sac, a process essential for sexual reproduction. Interaction between pollen and stigma (pollination) initiates secretion in the stigma and pollen germination. The pollen tube emerges and grows through the style to the ovaries where it delivers the sperm cells to the ovule to accomplish fertilization (Box 1) (Edlund et al., 2004). In Arabidopsis, the male gametophyte consists of three cells – one vegetative cell that encloses two sperm cells. Despite this seemingly simple system, about half of all Arabidopsis genes are expressed in pollen (Bock et al., 2006). There has been much recent progress in the field of pollen biology, especially in the area of pollen tube guidance and reception by the female gametophyte (reviewed by Kanaoka and Higashiyama, 2015). Pollen tubes have been studied intensively as a model system for tip growth, a process vital in diverse cell types from fungal hyphae to cancer cells (Sanati and Geitmann, 2013). Basic research on pollen biology also has many direct practical applications. The vast majority of the world’s harvest depends upon successful plant reproduction. In many crop plants the male gametophyte is sensitive to environmental stress, such as heat and drought, which can lead to serious crop losses (Zinn et al., 2010). Understanding pollen function is therefore also of important practical interest.

Proteome analysis of pollen in the K-type male sterility line 732A and its maintainer 732B in wheat (Triticum aestivum L.) by two-dimensional gel electrophoresis

Male sterility, especially cytoplasmic male sterility (CMS) where no functional pollen is produced, plays an important role in wheat breeding. Some specific proteins are related to male sterility in wheat, especially those present in pollen. To elucidate these sterility-related proteins, we applied two-dimensional gel electrophoresis (2-DE) to the proteomic analysis of pollen from a CMS line (732A) and its maintainer (732B) in wheat (Triticum aestivum L.), where trichloroacetic acid/acetone precipitation was used to extract pollen proteins from the wheat anthers. Analysis using PDQuest detected >350 reproducible protein spots on each 2-DE gel, where pI 4–7. In total, 41 spots were found to be differentially expressed, where 7/41 were identified by MALDI TOF/TOF–mass spectrometry analysis and protein database searching. The proteins comprised NADPH-producing dehydrogenase in the oxidative pentose phosphate pathway, cinnamyl alcohol dehydrogenase, cytosolic 3-phosphoglycerate kinase, caffeic acid O-methyltransferase, ascorbate peroxidase, glutamine synthetase isoform GS1a, and one unknown protein. In the uninucleate stage, all of the identified protein spots were downregulated in 732A, except the unknown protein, whereas there were no obvious differences in 732B. In the binucleate stage, the expression level of glutamine synthetase isoform GS1a did not differ between 732A and 732B, but caffeic acid O-methyltransferase was downregulated in 732A and the other five proteins were upregulated in 732A. These results suggest that male sterility in 732A is related to energy metabolism perturbation, active oxygen accumulation, programmed cell death, the pentose phosphate pathway, and glycolysis.

Mitochondrial ORF79 levels determine pollen abortion in cytoplasmic male sterile rice

Cytoplasmic male sterility (CMS) is an important agricultural trait characterized by lack of functional pollen, and caused by ectopic and defective mitochondrial gene expression. The pollen function in CMS plants is restored by the presence of nuclear-encoded restorer of fertility (Rf) genes. Previously, we cloned Rf2, which restores the fertility of Lead Rice (LD)-type CMS rice. However, neither the function of Rf2 nor the identity of the mitochondrial gene causing CMS has been determined in LD-CMS rice. Here, we show that the mitochondrial gene orf79 acts as a CMS-associated gene in LD-CMS rice, similar to its role in BT-CMS rice originating from Chinsurah Boro II, and Rf2 weakly restores fertility in BT-CMS rice. We also show that RF2 promotes degradation of atp6-orf79 RNA in a different manner from that of RF1, which is the Rf gene product in BT-CMS rice. The amount of ORF79 protein in LD-CMS rice was one-twentieth of the amount in BT-CMS rice. The difference in ORF79 protein levels probably accounts for the mild and severe pollen defects in LD-CMS and BT-CMS rice, respectively. In the presence of Rf2, accumulation of ORF79 was reduced to almost zero and 25% in LD-CMS and BT-CMS rice, respectively, which probably accounts for the complete and weak fertility restoration abilities of Rf2 in LD-CMS and BT-CMS rice, respectively. These observations indicate that the amount of ORF79 influences the pollen fertility in two strains of rice in which CMS is induced by orf79.

Pollen structure and function in caesalpinioid legumes

A diverse range of pollen morphologies occurs within the large, paraphyletic legume subfamily Caesalpinioideae, especially among early-branching lineages. Previous studies have hypothesized an association between surface ornamentation and pollination syndrome or other aspects of pollen function such as desiccation tolerance and adaptations to accommodate volume changes. We reviewed caesalpinioid pollen morphology using light microscopy, scanning and transmission electron microscopy, in combination with a literature survey of pollination vectors. Pollen structural diversity is greatest in the early-branching tribes Cercideae and Detarieae, whereas Cassieae and Caesalpinieae are relatively low in pollen diversity. Functional structures to counter desiccation include opercula (lids) covering apertures and reduced aperture size. Structures preventing wall rupture during dehydration and rehydration include different forms of colpi (syncolpi, parasyncolpi, pseudocolpi), striate supratectal ornamentation, and columellate or granular wall structures that resist tensile or compressive forces respectively. Specialized aperture structures (Zwischenkörper) may be advantageous for efficient germination of the pollen tube. In Detarieae and Cercideae in particular, there is potential to utilize pollen characters to estimate pollination systems where these are unknown. Supratectal verrucae and gemmae have apparently evolved iteratively in Cercideae and Detarieae. At the species level, there is a potential correlation between striate/verrucate patterns and vertebrate pollination.

Importance of organellar proteins, protein translocation and vesicle transport routes for pollen development and function.

Protein translocation. Cellular homeostasis strongly depends on proper distribution of proteins within cells and insertion of membrane proteins into the destined membranes. The latter is mediated by organellar protein translocation and the complex vesicle transport system. Considering the importance of protein transport machineries in general it is foreseen that these processes are essential for pollen function and development. However, the information available in this context is very scarce because of the current focus on deciphering the fundamental principles of protein transport at the molecular level. Here we review the significance of protein transport machineries for pollen development on the basis of pollen-specific organellar proteins as well as of genetic studies utilizing mutants of known organellar proteins. In many cases these mutants exhibit morphological alterations highlighting the requirement of efficient protein transport and translocation in pollen. Furthermore, expression patterns of genes coding for translocon subunits and vesicle transport factors in Arabidopsis thaliana are summarized. We conclude that with the exception of the translocation systems in plastids-the composition and significance of the individual transport systems are equally important in pollen as in other cell types. Apparently for plastids only a minimal translocon, composed of only few subunits, exists in the envelope membranes during maturation of pollen. However, only one of the various transport systems known from thylakoids seems to be required for the function of the "simple thylakoid system" existing in pollen plastids. In turn, the vesicle transport system is as complex as seen for other cell types as it is essential, e.g., for pollen tube formation.

It is a matter of timing: asynchrony during pollen development and its consequences on pollen performance in angiosperms-a review.

Functional pollen is needed to successfully complete fertilization. Pollen is formed inside the anthers following a specific sequence of developmental stages, from microsporocyte meiosis to pollen release, that concerns microsporocytes/microspores and anther wall tissues. The processes involved may not be synchronous within a flower, an anther, and even a microsporangium. Asynchrony has been barely analyzed, and its biological consequences have not been yet assessed. In this review, different processes of pollen development and lifetime, stressing on the possible consequences of their differential timing on pollen performance, are summarized. Development is usually synchronized until microsporocyte meiosis I (occasionally until meiosis II). Afterwards, a period of mostly asynchronous events extends up to anther opening as regards: (1) meiosis II (sometimes); (2) microspore vacuolization and later reduction of vacuoles; (3) amylogenesis, amylolysis, and carbohydrate inter-conversion; (4) the first haploid mitosis; and (5) intine formation. Asynchrony would promote metabolic differences among developing microspores and therefore physiologically heterogeneous pollen grains within a single microsporangium. Asynchrony would increase the effect of competition for resources during development and pollen tube growth and also for water during (re)hydration on the stigma. The differences generated by developmental asynchronies may have an adaptive role since more efficient pollen grains would be selected with regard to homeostasis, desiccation tolerance, resilience, speed of (re)hydration, and germination. The performance of each pollen grain which landed onto the stigma will be the result of a series of selective steps determined by its development, physiological state at maturity, and successive environmental constrains.

Male functions and malfunctions: the impact of phosphoinositides on pollen development and pollen tube growth.

Phosphoinositides in pollen. In angiosperms, sexual reproduction is a series of complex biological events that facilitate the distribution of male generative cells for double fertilization. Angiosperms have no motile gametes, and the distribution units of generative cells are pollen grains, passively mobile desiccated structures, capable of delivering genetic material to compatible flowers over long distances and in an adverse environment. The development of pollen (male gametogenesis) and the formation of a pollen tube after a pollen grain has reached a compatible flower (pollen tube growth) are important aspects of plant developmental biology. In recent years, a wealth of information has been gathered about the molecular control of cell polarity, membrane trafficking and cytoskeletal dynamics underlying these developmental processes. In particular, it has been found that regulatory membrane phospholipids, such as phosphoinositides (PIs), are critical regulatory players, controlling key steps of trafficking and polarization. Characteristic features of PIs are the inositol phosphate headgroups of the lipids, which protrude from the cytosolic surfaces of membranes, enabling specific binding and recruitment of numerous protein partners containing specific PI-binding domains. Such recruitment is globally an early event in polarization processes of eukaryotic cells and also of key importance to pollen development and tube growth. Additionally, PIs serve as precursors of other signaling factors with importance to male gametogenesis. This review highlights the recent advances about the roles of PIs in pollen development and pollen function.

Post‐translational mechanisms are associated with fertility restoration of cytoplasmic male sterility in sugar beet (Beta vulgaris)

Genetic conflict between cytoplasmically inherited elements and nuclear genes arising from their different transmission patterns can be seen in cytoplasmic male sterility (CMS), the mitochondrion-encoded inability to shed functional pollen. CMS is associated with a mitochondrial open reading frame (ORF) that is absent from non-sterility inducing mitochondria (S-orf). Nuclear genes that suppress CMS are called restorer-of-fertility (Rf) genes. Post-transcriptional and translational repression of S-orf mediates the molecular action of Rf that encodes a class of RNA-binding proteins with pentatricopeptide repeat (PPR) motifs. Besides the PPR-type of Rfs, there are also non-PPR Rfs, but the molecular interactions between non-PPR Rf and S-orf have not been described. In this study, we investigated the interaction of bvORF20, a non-PPR Rf from sugar beet (Beta vulgaris), with preSatp6, the S-orf from sugar beet. Anthers expressing bvORF20 contained a protein that interacted with preSATP6 protein. Analysis of anthers and transgenic calli expressing a FLAG-tagged bvORF20 suggested the binding of preSATP6 to bvORF20. To see the effect of bvORF20 on preSATP6, which exists as a 250-kDa protein complex in CMS plants, signal bands of preSATP6 in bvORF20-expressing and non-expressing anthers were compared by immunoblotting combined with Blue Native polyacrylamide gel electrophoresis. The signal intensity of the 250-kDa band decreased significantly, and 200- and 150-kDa bands appeared in bvORF20-expressing anthers. Transgenic callus expressing bvORF20 also generated the 200- and 150-kDa bands. The 200-kDa complex is likely to include both preSATP6 and bvORF20. Post-translational interaction between preSATP6 and bvORF20 appears to alter the higher order structure of preSATP6 that may lead to fertility restoration in sugar beet.

Characterization and genetic mapping of a novel recessive genic male sterile gene ms305 in maize (Zea mays L.)

The male sterility system shows tremendous value for the long-term utilization of hybrid crop breeding. In this study, a male sterile mutant,K305ms, was derived from the M3progeny of maize (Zea maysL.) inbred line K305 exposed to60Co-γ irradiation. Male sterileK305msplants did not show any obvious differences from their sibling male fertile plants (K305F) during the vegetative stage, but failed to produce functional pollen at the reproductive stage. Microscopic observations determined that the dyads and tetrads from the pollen ofK305msplants developed abnormally, and subsequently the microspores were shriveled. Genetic analysis indicated that the male sterility ofK305mswas controlled by a single recessive genic gene. Gene mapping showed that the responsible gene was located between two simple sequence repeat markers on chromosome 2L in a region of 10.3 cM, bnlg469b and bnlg1940, with genetic distances of 2.9 and 7.4 cM, respectively. According to the microscopic and mapping characteristics, our results showed that this gene was distinguishable from all other reported male sterile genes in maize, and it is temporarily designated asms305. The linkage map in this study will provide a useful fundamental basis for molecular marker-assisted selection as well as for further map-based cloning ofms305.

Molecular characterization and application of a novel cytoplasmic male sterility-associated mitochondrial sequence in rice.

BackgroundCytoplasmic male sterility (CMS) is a maternally inherited inability to produce functional pollen found in numerous flowering plant species. CMS is associated with mitochondrial DNA mutation, novel chimeric open reading frames (ORFs), and rearrangement of coding and noncoding regions of the mitochondrial genome.ResultsBLAST (Basic Local Alignment Search Tool) analysis indicated that L-sp1, a new sequence-characterized amplified region, is non-homologous to atp6-orfH79 (or atp6-orf79) and WA352 cloned CMS-associated genes. L-sp1 was found in 11 of 102 wild rice accessions belonging to four AA genome species: Oryza rufipogon, Oryza nivara, Oryza glumaepatula, and Oryza meridionalis. Using L-sp1, two new CMS lines were developed, from either low natural fertility plants or sterile plants, by backcrossing BC1F1 with Yuetai B. Northern blot and RT-PCR revealed that L-sp1 was only expressed in the anthers of w1/YTB, w2/YTB, w1/YTB//YTB, and w2/YTB//YTB when in the same cytoplasm background.ConclusionsL-sp1 is a single-copy chimeric CMS-associated gene found in the mitochondrial genome. It can be expressed in anthers with the same specific cytoplasm background, and will be a useful molecular marker for the development and marker-assisted selection of new CMS lines.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0205-0) contains supplementary material, which is available to authorized users.

A decade of pollen transcriptomics.

Key message Overview of pollen transcriptome studies. Pollen development is driven by gene expression, and knowledge of the molecular events underlying this process has undergone a quantum leap in the last decade through studies of the transcriptome. Here, we outline historical evidence for male haploid gene expression and review the wealth of pollen transcriptome data now available. Knowledge of the transcriptional capacity of pollen has progressed from genetic studies to the direct analysis of RNA and from gene-by-gene studies to analyses on a genomic scale. Microarray and/or RNA-seq data can now be accessed for all phases and cell types of developing pollen encompassing 10 different angiosperms. These growing resources have accelerated research and will undoubtedly inspire new directions and the application of system-based research into the mechanisms that govern the development, function and evolution of angiosperm pollen.Electronic supplementary materialThe online version of this article (doi:10.1007/s00497-015-0261-7) contains supplementary material, which is available to authorized users.

The role of UV-B radiation in plant sexual reproduction

UV-B radiation affects plant sexual reproduction, but, at present, general patterns about the nature of these effects and their underlying mechanisms remain elusive. In recent years, plant UV-B research has experienced a substantial conceptual change, from a stress-dominated view towards a more regulatory perspective. With this in mind, we have surveyed the published literature on the effects of UV-B radiation on plant reproductive traits and on plant–pollinator interactions. Most floral parts are effectively UV-B protected thanks to the accumulation of UV-B absorbing compounds. However, the least protected parts, such as pollen, are sensitive to high UV-B doses. Among UV-B absorbing compounds, flavonoids have a complex role in plant reproduction, since they are essential for UV-B protection and normal pollen function, while they also modulate flower and fruit colouration, which, in turn, affects visits by pollinators and frugivores. Effects of UV-B radiation on pollination can be direct, due to UV-B effects on pollinators, or indirect, due to pollinators responding to UV-B-mediated changes in plants. In the case of annual species, our literature survey revealed that, as UV-B doses increase, there is a tendency to delay the onset of flowering and to decrease fruit and/or seed production. Yet, the present review highlights the existence of complex dose–response curves that emphasize the need to use multiple UV-B doses in future studies of UV-B-mediated flowering responses. Moreover, species, populations or even cultivars originating from geographical areas with high impact of solar radiation (e.g. Mediterranean Basin) exhibit, in general, high protection against UV-B radiation, often showing positive responses to moderate UV-B increases. In conclusion, our survey of the literature reveals complex UV-B effects on plant reproduction. To fully comprehend these effects, integrated approaches, beyond those currently used, are required to analyze the complex mixture of direct and indirect, stimulatory and inhibitory UV-B responses.