Male Fertility Control Research Articles

Molecular Control of Male Fertility for Crop Hybrid Breeding.

In many plant species, male-sterile female lines with cytoplasmic male sterility (CMS) or nuclear-controlled environment-sensitive genic male sterility (EGMS) have long been used to efficiently produce hybrids that harness hybrid vigor or heterosis. However, the underlying molecular mechanisms for these applications have only recently been uncovered in a few species. We provide here an update on the understanding of cytoplasmic-nuclear communication based on the discovery of mitochondrial CMS genes and their corresponding nuclear fertility determinants. Recent findings that uncover diverse mechanisms such as epigenetic, transcriptional, and post-transcriptional controls of EGMS by temperature and photoperiod signals are also reviewed. Furthermore, translational research that applies basic knowledge of plant male fertility control to hybrid seed production practice is highlighted.

Chromosomes 1BS and 1RS for control of male fertility in wheats and triticales with cytoplasms of Aegilops kotschyi, Ae. mutica and Ae. uniaristata.

Engineered chromosomes 1BS and 1RS offer a new alternative in the development of hybrid systems in bread wheat and triticale. In the cytoplasmic male sterility system for hybrid wheat based on the cytoplasm of Triticum timopheevi fertility restoration is difficult, with few good restorer genes available. In the system based on the cytoplasms of Aegilops kotschyi, Ae. uniaristata and Ae. mutica, essentially all chromosomes 1B carry locus Rf multi that restores male fertility; male sterility manifests itself in wheats with the 1RS.1BL translocation where 1BS chromosome arm is missing. To generate male sterile wheats without the 1RS.1BL translocation, the 1BS arm was cytogenetically engineered to replace the segment with Rf multi with two short inserts of rye chromatin. Conversely, to enhance fertility restoration by doubling the number of restorers present for eventual use in wheat and triticale, a region of 1BS with Rf multi was inserted into 1RS. Alloplasmic wheats with Rf multi removed were completely male sterile; alloplasmic wheats with engineered 1RS carrying Rf multi and without normal 1B were male fertile. An exception to the ubiquitous presence of Rf multi is T. spelta var. duhamelianum; four accessions tested in this study gave inconsistent results but some did not restore male fertility. Engineered chromosomes 1BS and 1RS and chromosomes 1B of T. spelta offer a new alternative for practical application of a cytoplasmic male sterility system in the development of hybrid wheat and hexaploid triticale.

MicroRNAs in Sertoli cells: implications for spermatogenesis and fertility.

In recent decades, infertility has been considered a major widespread public health issue of very high concern. Currently, almost 50% of infertility cases are due to male factors, including semen disorders, obstructions, cryptorchidism, varicocele and testicular failures, which can occur due to malfunctions in both somatic and germ cells. In this context, besides other approaches, different miRNAs have been used as biomarkers for the diagnosis of male infertility, with different pathologic conditions such as Sertoli cell-only syndrome, mixed atrophy, and germ cell arrest. However, most studies related to male fertility do not point out the functions and cell targets of the described miRNAs. Initial investigations using experimental assays in murine and porcine models were performed, providing the first evidence of the influence of miRNAs on Sertoli cell function including, for instance, proliferation, maturation and hormone responses of these cells. The aim of this mini-review is therefore to summarize our present knowledge of this relevant subject and to highlight the importance of future investigations concerning the miRNA influence in the control of Sertoli cells, spermatogenesis and male fertility.

Kisspeptins, Estrogens and Male Fertility.

The control of male fertility requires accurate endocrine, paracrine and autocrine communications along the hypothalamus-pituitary-gonad (HPG) axis. In this respect, the possible interplay between upcoming/classical modulators of reproductive functions deserves attention in that may be a successful tool for the future exploitation of new potential therapeutic targets in the treatment of fertility disorders. In this review we will discuss upcoming data concerning the role of kisspeptins, the products of the Kiss1 gene, and estrogens - classically considered as female hormones - as well as their possible interplay in testis. Kisspeptins, via the activation of kisspeptin receptor Gpr54 represent the main gatekeeper of the hypothalamic Gonadotropin Releasing Hormone (GnRH) centrally modulating the onset and maintaining reproductive functions. As a consequence, the loss of kisspeptin signalling causes hypogonadotrophic hypogonadism in humans and animal models. In spite of the well recognized functions at hypothalamic levels, recent data strongly support direct production and activity of kisspeptin in testis and its involvement in the control of Leydig cells, germ cells progression and sperm functions. Similarly, estrogens exhibit high impact on proliferative/apoptotic/differentiative events in testis, thus resulting as local key modulators for the production - but also for the release, transport and maturation - of high quality spermatozoa. This review summarizes the upcoming data from experimental models and humans concerning the testicular activity of kisspeptins and estrogens to preserve male fertility. Mutual enhancement of kisspeptin and estradiol signalling for the progression of spermatogenesis has also been discussed.

The control of male fertility by spermatid-specific factors: searching for contraceptive targets from spermatozoon's head to tail.

Male infertility due to abnormal spermatozoa has been reported in both animals and humans, but its pathogenic causes, including genetic abnormalities, remain largely unknown. On the other hand, contraceptive options for men are limited, and a specific, reversible and safe method of male contraception has been a long-standing quest in medicine. Some progress has recently been made in exploring the effects of spermatid-specifical genetic factors in controlling male fertility. A comprehensive search of PubMed for articles and reviews published in English before July 2016 was carried out using the search terms ‘spermiogenesis failure', ‘globozoospermia', ‘spermatid-specific', ‘acrosome', ‘infertile', ‘manchette', ‘sperm connecting piece', ‘sperm annulus', ‘sperm ADAMs', ‘flagellar abnormalities', ‘sperm motility loss', ‘sperm ion exchanger' and ‘contraceptive targets'. Importantly, we have opted to focus on articles regarding spermatid-specific factors. Genetic studies to define the structure and physiology of sperm have shown that spermatozoa appear to be one of the most promising contraceptive targets. Here we summarize how these spermatid-specific factors regulate spermiogenesis and categorize them according to their localization and function from spermatid head to tail (e.g., acrosome, manchette, head-tail conjunction, annulus, principal piece of tail). In addition, we emphatically introduce small-molecule contraceptives, such as BRDT and PPP3CC/PPP3R2, which are currently being developed to target spermatogenic-specific proteins. We suggest that blocking the differentiation of haploid germ cells, which rarely affects early spermatogenic cell types and the testicular microenvironment, is a better choice than spermatogenic-specific proteins. The studies described here provide valuable information regarding the genetic and molecular defects causing male mouse infertility to improve our understanding of the importance of spermatid-specific factors in controlling fertility. Although a male contraceptive ‘pill' is still many years away, research into the production of new small-molecule contraceptives targeting spermatid-specific proteins is the right avenue.

Role of Dicer1-Dependent Factors in the Paracrine Regulation of Epididymal Gene Expression.

Dicer1 is an endoribonuclease involved in the biogenesis of functional molecules such as microRNAs (miRNAs) and endogenous small interfering RNAs (endo-siRNAs). These small non-coding RNAs are important regulators of post-transcriptional gene expression and participate in the control of male fertility. With the knowledge that 1) Dicer1-dependent factors are required for proper sperm maturation in the epididymis, and that 2) miRNAs are potent mediators of intercellular communication in most biological systems, we investigated the role of Dicer1-dependent factors produced by the proximal epididymis (initial segment/caput)- including miRNAs- on the regulation of epididymal gene expression in the distal epididymis regions (i.e. corpus and cauda). To this end, we performed comparative microarray and ANOVA analyses on control vs. Defb41iCre/wt;Dicer1fl/fl mice in which functional Dicer1 is absent from the principal cells of the proximal epididymis. We identified 35 and 33 transcripts that displayed significant expression level changes in the corpus and cauda regions (Fold change > 2 or < −2; p < 0.002), respectively. Among these transcripts, Zn-alpha 2-glycoprotein (Azgp1) encodes for a sperm equatorial protein whose expression in the epididymis of Dicer1 cKO mice is significantly increased compared to controls. In addition, 154 miRNAs, including miR-210, miR-672, miR-191 and miR-204, showed significantly impaired biogenesis in the absence of Dicer1 from the principal cells of the proximal epididymis (Fold change > 2 or < −2; p < 0.01). These miRNAs are secreted via extracellular vesicles (EVs) derived from the DC2 epididymal principal cell line, and their expression correlates with target transcripts involved in distinct biological pathways, as evidenced by in silico analysis. Albeit correlative and based on in silico approach, our study proposes that Dicer1-dependent factors trigger- directly or not—significant genes expression changes in distinct regions of this organ. The paracrine control of functions important to post-testicular sperm maturation by Dicer1-dependent factors may open new avenues for the identification of molecular targets important to male fertility control.

SOX9 regulates expression of the male fertility gene Ets variant factor 5 (ETV5) during mammalian sex development

In humans, dysregulation of the sex determining gene SRY-box 9 (SOX9) leads to disorders of sex development (DSD). In mice, knock-out of Sox9 prior to sex determination leads to XY sex reversal, while Sox9 inactivation after sex determination leads to spermatogenesis defects. SOX9 specifies the differentiation and function of Sertoli cells from somatic cell precursors, which then orchestrate the development and maintenance of other testicular cell types, largely through unknown mechanisms. Here, we describe a novel testicular target gene of SOX9, Ets variant factor 5 (ETV5), a transcription factor responsible for maintaining the spermatogonial stem cell niche. Etv5 was highly expressed in wild-type XY but not XX mouse fetal gonads, with ETV5 protein localized in the Sertoli cells, interstitial cells and germ cells of the testis. In XY Sox9 knock-out gonads, Etv5 expression was strongly down-regulated. Similarly, knock-down of SOX9 in the human Sertoli-like cell line NT2/D1 caused a decrease in ETV5 gene expression. Transcriptomic analysis of NT2/D1 cells over-expressing SOX9 showed that ETV5 expression was increased in response to SOX9. Moreover, chromatin immunoprecipitation of these cells, as well as of embryonic mouse gonads, showed direct binding of SOX9 to ETV5 regulatory regions. We demonstrate that SOX9 was able to activate ETV5 expression via a conserved SOX site in the 5′ regulatory region, mutation of which led to loss of activation. In conclusion, we present a novel target gene of SOX9 in the testis, and suggest that SOX9 regulation of ETV5 contributes to the control of male fertility.

AMPK, regulator of sperm energy and functions

The 5'-AMP-activated protein kinase, AMPK, is a key protein kinase in the metabolism of the cell that regulates many metabolic pathways. The involvement of cell metabolism in sperm ability to fertilize is well established, but only a few studies have focused on the role of AMPK in the control of male fertility. This article summarizes the known role of AMPK in this area. AMPK is involved in the regulation of sperm quality by its action on the proliferation of Sertoli cells. AMPK also directly controls the quality of sperm by its involvement in the regulation of motility and acrosome reaction. It is also involved in the management of lipid peroxidation and gametes antioxidant enzymes. Thus, AMPK appears as a key signaling protein for sperm and male fertility control.

Identification of the tethered peptide agonist of the adhesion G protein-coupled receptor GPR64/ADGRG2

The epididymis-specific adhesion G protein-coupled receptor (aGPCR) GPR64/ADGRG2 has been shown to be a key-player in the male reproductive system. As its disruption leads to infertility, GPR64 has drawn attention as potential target for male fertility control or improvement. Like the majority of aGPCRs GPR64 is an orphan receptor regarding its endogenous agonist and signal transduction. In this study we examined the G protein-coupling abilities of GPR64 and showed that it is activated through a tethered agonist sequence, which we have previously identified as the Stachel sequence. Synthetic peptides derived from the Stachel region can activate the receptor, opening for the first time the possibility to externally manipulate the receptor activity.

Metabolic cooperation in testis as a pharmacological target: from disease to contraception.

The development of a "male pill" to control fertility is still a major challenge. Although women have several options to play an active role in the couple family planning, men are very limited in terms of contraceptive methods. Several approaches have been proposed to develop a male contraceptive and can be divided in two major groups: hormonal and non-hormonal methods. Within the testis, the somatic Sertoli cell (SC) is known as the "nurse cell" since it provides the physical and nutritional support for the developing germ cells. Moreover, adjacent SCs form the Sertoli/blood testis barrier (BTB), which divides the seminiferous epithelium into the basal and the apical compartments, controlling the passage of substances to the site where germ cells develop. Among the several functions of SC, its metabolism and the production of lactate, acetate and other metabolic factors are essential for the normal occurrence of spermatogenesis. In the last years, several works have highlighted that the metabolic cooperation established between SCs and developing germ cells is compromised in several diseases associated with male subfertility/infertility. Notably, several metabolismassociated proteins are specifically expressed in the testis. Thus, there are several evidences illustrating that the control of male fertility can be achieved by targeting testicular cells metabolism. Herein, we discuss the metabolic cooperation in testis as a potential pharmacological target to counteract subfertility/infertility promoted by several diseases, particularly metabolic diseases. We also discuss how it can contribute to the development of a male contraceptive.

Extracellular microRNAs from the epididymis as potential mediators of cell-to-cell communication.

Ribonucleic acid (RNA) was previously thought to remain inside cells as an intermediate between genes and proteins during translation. However, it is now estimated that 98% of the mammalian genomic output is transcribed as noncoding RNAs, which are involved in diverse gene expression regulatory mechanisms and can be transferred from one cell to another through extracellular communication. For instance, microRNAs are 22-nucleotide-long noncoding RNAs that are generated by endonuclease cleavage of precursors inside the cells and are secreted as extracellular microRNAs to regulate target cell posttranscriptional gene expression via RNA interference. We and others have shown that different populations of microRNAs are expressed in distinct regions of the human epididymis and regulate the expression of target genes that are involved in the control of male fertility as indicated by knock-out mouse models. Importantly, some microRNAs, including the microRNA-888 (miR-888) cluster that is exclusively expressed in the reproductive system of human and nonhuman primates, are released in the sperm-surrounding fluid in the epididymis via extracellular vesicles, the so-called epididymosomes. In addition to interacting with the membrane of maturing spermatozoa, these extracellular vesicles containing microRNAs communicate with epithelial cells located downstream from their release site, suggesting a role in the luminal exocrine control of epididymal functions. Apart from their potential roles as mediators of intercellular communication within the epididymis, these extracellular microRNAs are potent molecular targets for the noninvasive diagnosis of male infertility.

Adaptive Regulation of Testis Gene Expression and Control of Male Fertility by the Drosophila Hairpin RNA Pathway

Although endogenous siRNAs (endo-siRNAs) have been described in many species, still little is known about their endogenous utility. Here, we show that Drosophila hairpin RNAs (hpRNAs) generate an endo-siRNA class with predominant expression in testes. Although hpRNAs are universally recently evolved, we identify highly complementary protein-coding targets for all hpRNAs. Importantly, we find broad evidence for evolutionary divergences that preferentially maintain compensatory pairing between hpRNAs and targets, serving as first evidence for adaptive selection for siRNA-mediated target regulation in metazoans. We demonstrate organismal impact of hpRNA activity, since knockout of hpRNA1 derepresses its target ATP synthase-β in testes and compromises spermatogenesis and male fertility. Moreover, we reveal surprising male-specific impact of RNAi factors on germ cell development and fertility, consistent with testis-directed function of the hpRNA pathway. Finally, the collected hpRNA loci chronicle an evolutionary timeline that reflects their origins from prospective target genes, mirroring a strategy described for plant miRNAs.

Importance of Male Fertility Control in Family Planning

The world population, currently estimated to be almost seven billion, is expected to double in less than four decades. The projected population growth will cause severe competition for existing resources, not to mention the issue of overcrowding of the planet and additional greenhouse gases that will have an adverse effect on the ecological health of the planet. A recent survey conducted by the United Nations Population Control Division shows that the majority of today's young men in many countries are willing to participate in family planning by taking full control of their fertility, an important global health issue. However, the contraceptive needs of tens of millions of men/couples go unmet every single day and results in millions of unwanted pregnancies. Ever since the approval of the birth control pill by the Food and Drug Administration (FDA) in 1960, scientists have been hoping for a male equivalent. It has, however, been a difficult road, in part because of the complicated science of the male reproductive system. It is easier to control a monthly event of ovulation in women than to regulate the production of millions of fertile spermatozoa every day in men. Thus, the contraceptive options for men have not changed in decades and are still limited to the use of condoms, a timely withdrawal/pulling out (coitus interruptus) or vasectomy, a minor surgical procedure in which the vas deferens is occluded to prevent the release of spermatozoa during ejaculation. The first two approaches have a relatively higher failure rate, whereas the last approach is largely irreversible and not suitable for younger men. In this article, we will discuss various approaches currently available for men to take control of their fertility. Our intention is to discuss the details of three similar approaches that will provide safe, affordable and reversible contraception for men and are close to being approved for use by millions of men around the globe. The availability of safe, reversible and reliable male contraceptives will allow men and women to take full control of their fertility in family planning.

VASECTOMÍA SIN BISTURÍ: RESULTADOS DE UNA COHORTE DE 309 PACIENTES

No-scalpel vasectomy Introduction: Vasectomy is a safe and effective technique of male fertility control. Despite this, in the world are carried out more than double female sterilization in comparison with vasectomies, that is more pronounced in less developed countries. Aims: To present our experience and results in patients undergoing a no-scalpel vasectomy. Methods and Material: A total of 309 patients undergoing a no-scalpel vasectomy between June 2009 and May 2010 were included. For each case was record age, operative time, sperm count at 3 months post vasectomy and peri-operative morbidity. Results: 309 vasectomies were performed, 281 patients (91%) were controlled with at least one sperm count. Azoospermia was obtained in the first sperm count at 3 months in 189 patients (67%). In 81 patients (29%) were observed ≤ 100,000 sperm 100% immo- bile. 9 patients (3.2%) needed a second semen analysis and 2 patients a third one for less than 100,000 sperm that were 100% immobile. 6 patients (2%) consulted by minor complications such as postoperative pain, epididymitis or hematoma with spontaneous resolution. Conclusions: Vasectomy is a safe and reproducible method of male contraception, presenting an effectiveness rates higher than others contraceptive methods. There are no absolute contraindications for performing the procedure. A sperm count should be done at 3 months of the procedure. The early failure rate in our study is 0.3%.

A barleyPHDfinger transcription factor that confers male sterility by affecting tapetal development

Controlling pollen development is of major commercial importance in generating hybrid crops and selective breeding, but characterized genes for male sterility in crops are rare, with no current examples in barley. However, translation of knowledge from model species is now providing opportunities to understand and manipulate such processes in economically important crops. We have used information from regulatory networks in Arabidopsis to identify and functionally characterize a barley PHD transcription factor MALE STERTILITY1 (MS1), which expresses in the anther tapetum and plays a critical role during pollen development. Comparative analysis of Arabidopsis, rice and Brachypodium genomes was used to identify conserved regions in MS1 for primer design to amplify the barley MS1 gene; RACE-PCR was subsequently used to generate the full-length sequence. This gene shows anther-specific tapetal expression, between late tetrad stage and early microspore release. HvMS1 silencing and overexpression in barley resulted in male sterility. Additionally, HvMS1cDNA, controlled by the native Arabidopsis MS1 promoter, successfully complemented the homozygous ms1 Arabidopsis mutant. These results confirm the conservation of MS1 function in higher plants and in particular in temperate cereals. This has provided the first example of a characterized male sterility gene in barley, which presents a valuable tool for the future control of male fertility in barley for hybrid development.

Inhibiting Human Lactate Dehydrogenase-C for Male Fertility Control; Initial Hits

Lactate dehydrogenase-C (LDH-C) is an oxido-reductive enzyme of LDH (EC 1.1.1.27) family which is present abundantly in testes, spermatocytes, spermatids and sperms. It plays an important role in maintaining glycolysis and ATP production in the flagellum during sperm capacitation, therefore essential for male fertility. Profuse expression exclusively in these tissues makes LDH-C a potential target for male contraceptive development. However, creating a specific inhibitor for LDH-C is challenging due to its extensive sequence similarity (84-89%) with somatic isozymes LDH-A and B.

Tapetum and middle layer control male fertility in Actinidia deliciosa

Background and AimsDioecism characterizes many crop species of economic value, including kiwifruit (Actinidia deliciosa). Kiwifruit male sterility occurs at the microspore stage. The cell walls of the microspores and the pollen of the male-sterile and male-fertile flowers, respectively, differ in glucose and galactose levels. In numerous plants, pollen formation involves normal functioning and degeneration timing of the tapetum, with calcium and carbohydrates provided by the tapetum essential for male fertility. The aim of this study was to determine whether the anther wall controls male fertility in kiwifruit, providing calcium and carbohydrates to the microspores.MethodsThe events occurring in the anther wall and microspores of male-fertile and male-sterile anthers were investigated by analyses of light microscopy, epifluorescence, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL assay) and transmission electron microscopy coupled with electron spectroscopy. The possibility that male sterility was related to anther tissue malfunctioning with regard to calcium/glucose/galactose provision to the microspores was also investigated by in vitro anther culture.Key ResultsBoth tapetum and the middle layer showed secretory activity and both degenerated by programmed cell death (PCD), but PCD was later in male-sterile than in male-fertile anthers. Calcium accumulated in cell walls of the middle layer and tapetum and in the exine of microspores and pollen, reaching higher levels in anther wall tissues and dead microspores of male-sterile anthers. A specific supply of glucose and calcium induced normal pollen formation in in vitro-cultured anthers of the male-sterile genotype.ConclusionsThe results show that male sterility in kiwifruit is induced by anther wall tissues through prolonged secretory activity caused by a delay in PCD, in the middle layer in particular. In vitro culture results support the sporophytic control of male fertility in kiwifruit and open the way to applications to overcome dioecism and optimize kiwifruit production.

Control of Male and Female Fertility by the Netrin Axon Guidance Genes

The netrin axon guidance genes have previously been implicated in fertility in C. elegans and in vertebrates. Here we show that adult Drosophila lacking both netrin genes, NetA and NetB, have fertility defects in both sexes together with an inability to fly and reduced viability. NetAB females produce fertilized eggs at a much lower rate than wild type. Oocyte development and ovarian innervation are unaffected in NetAB females, and the reproductive tract appears normal. A small gene, hog, that resides in an intron of NetB does not contribute to the NetAB phenotype. Restoring endogenous NetB expression rescues egg-laying, but additional genetic manipulations, such as restoration of netrin midline expression and inhibition of cell death have no effect on fertility. NetAB males induce reduced egg-laying in wild type females and display mirror movements of their wings during courtship. Measurement of courtship parameters revealed no difference compared to wild type males. Transgenic manipulations failed to rescue male fertility and mirror movements. Additional genetic manipulations, such as removal of the enabled gene, a known suppressor of the NetAB embryonic CNS phenotype, did not improve the behavioral defects. The ability to fly was rescued by inhibition of neuronal cell death and pan-neural NetA expression. Based on our results we hypothesize that the adult fertility defects of NetAB mutants are due to ovulation defects in females and a failure to properly transfer sperm proteins in males, and are likely to involve multiple neural circuits.

Role of Glutathione in Male Infertility

Infertility is a worldwide problem and in almost 50% of cases infertility results from abnormality of the male partners. Apart from endocrine disorders, definitive cause and mechanism of male infertility is not clear in many cases. Recent evidence indicates that imbalance between pro-oxidant stress and antioxidant defense plays an important role in the pathogenesis of male infertility. Among the endogenous antioxidant systems, reduced glutathione (GSH) plays a significant role in the antioxidant defense of the spermatogenic epithelium, the epididymis and perhaps in the ejaculated spermatozoa. The current study was therefore designed to evaluate any association that may exist between GSH levels and male infertility. Infertile male patients (having female partners with normal fertility parameters; n=31) and age- matched healthy male fertile control subjects (n=30) were included in this study. In addition to medical history, semen analyses including semen volume, sperm count, motility and morphology were done for each subject. As a measure of antioxidant capacity erythrocyte and seminal plasma GSH concentrations were measured by Ellman's method in fertile and infertile male subjects. The infertile subjects were similar to fertile subjects in terms of age. However, semen volume and sperm count was found significantly lower (p&lt;0.001) in infertile males compared with healthy fertile male subjects. Percentage of subjects with abnormal sperm morphology and motility were found higher in infertile group compared with fertile group. The median (range) erythrocyte GSH level did not differ between the two groups (12.62 (0.67-29.82) versus 13.93 (2.10-21.08) mg/gm Hb). However, the seminal plasma GSH level was found markedly suppressed in infertile group (1.64 (0.23-7.50)) compared with fertile group (4.26 (2.32-7.50)) mg/dl (p&lt;0.001). In the present study seminal plasma GSH level was found markedly suppressed along with abnormal values for semen volume, sperm concentration and sperm morphology and motility in infertile subjects compared with fertile subjects. This finding indicates that low level of seminal plasma GSH level may be associated with male infertility. DOI: http://dx.doi.org/10.3329/bjmb.v4i2.13772 Bangladesh J Med Biochem 2011; 4(2): 20-25

Inter-Conversion of Carbohydrate Reserves from Pollen Maturation to Rehydration in a Chili Pepper

Carbohydrate metabolism is critical for male fertility. Carbohydrate reserves (soluble sugars and starch) were quantified in three advanced stages of pollen development, from the final maturation to rehydration, in a chili pepper cultivar (Capsicum annuum L. cv. Calypso Red) with partially dehydrated pollen, to define possible carbohydrate inter-conversions. At the same time, the activity of soluble enzymes involved in sucrolysis and amylolysis were quantified to reveal potential metabolic pathways. The carbohydrates found (sucrose, glucose, fructose, and starch) apparently inter-convert. There would be a close relation between enzymatic activities and substrates, and the carbohydrate reserves could be key factors on the regulation of enzymatic activities. All the enzymes tested were active, although the relevance of each one changed along pollen maturation and rehydration, defining different profiles of enzymatic activities for each stage. Some usually neglected enzymes (e.g. soluble neutral invertase) have shown an important role in the stages analyzed, suggesting alternative processes to evaluate in the studies of male fertility control.