Transcriptome Analysis Reveals Important Transcription Factor Families and Reproductive Biological Processes of Flower Development in Celery (Apium graveolens L.)

There are few reports on the reproductive biology of celery, which produces small flowers in a long flowering period. Anther development was analyzed by paraffin sectioning and related genes were examined by transcriptome sequencing and qPCR. The development process was divided into nine stages based on the significant changes in the cell and tissue morphologies. These stages included: archesporial stage, sporogenous cell stage, microspore mother cell stage, dyad and tetrad stage, mononuclear microspore stage, late uninucleate microspore stage, binuclear cell stage, mature pollen stage, and dehiscence stage. A total of 1074 differentially expressed genes were identified by transcriptome sequencing in the early flower bud, middle flower bud, and early flowering period. Functional annotation indicated that these genes were involved in physiological and biochemical processes such as ribosomes metabolism, sugar metabolism, and amino acid metabolism. Transcription factors such as C2H2, AP2/ERF, bZIP, WRKY, and MYB played key regulatory roles in anther development and had different regulatory capabilities at various stages. The expression patterns based on qPCR and transcriptome data of the selected transcription factor genes showed consistency, suggesting that these genes played an important role in different flower development stages. These results provide a theoretical basis for molecular breeding of new celery varieties with pollen abortion. Furthermore, they have enriched research on the reproductive biology of celery and the Apiaceae family.

Male gametophyte development steps in Pistacia vera L.

Sadeghirad E, Majd A, Iranbakhsh A, Javanshah A. 2018. Male gametophyte development steps in Pistacia vera L. Nusantara Bioscience 10: 151-158. Salinity affects the growth and development of plant. It also affects the development steps of male gametophyte in pistachio plant. Pistachio (Pistachio vera) is a member of family Anacardiaceae and order Sapindales. To study the effects of salinity on those steps, an experiment was performed in two locations in Golshan Anar with commensurate circumstances, namely: a control area (A) which was well-irrigated with fresh water, and the other area (B) which was well-irrigated with salty water added with NaCl solution with EC values of 14 dS.m-1. The flowers sampling was done in two Golshan Anar regions on the springtime based on a completely randomized design with three replications. The development steps of male gametophyte in pistachio plant were observed using conventional cell histology techniques and light microscopy observations and were then contrasted with samples subjected to no salinity stress. The results represented that several steps of male gametophyte development are as follows: (1) the anther experiencing normal growth which is tetrasporangiate, (2) cytokinesis taking place simultaneously with meiosis in the microspore mother cell, the tetrahedral tetrads, (3) microspores being delivered after meiosis by microsporogenesis were more or less irregular in shape during the contraction period. Finally, the abnormal shape and structure of the number of cases reviewed in three replicates of pollens can be one of the significant factors influencing the decline in the product.

The Effect of NaCl on Anther Development in Pistacia vera L.

Plant growth and development are adversely affected by salinity. In order to study the effects of salinity on male gametophyte development steps in pistachio plant, an experiment was conducted in two areas in Golshan Anar with equal conditions: a control area (A) that was irrigated with fresh water well, and the other area (B) with salty water and EC values 14 dS.m-1 NaCl solution. A sampling of flowers was performed in two areas of Golshan Anar in the spring based on a completely randomized design with three replications. Male gametophyte development steps in pistachio plant were examined using conventional cell histology techniques and light microscopy observations and were then compared with samples subjected to no salinity stress. The results showed that some stages of male gametophyte development: (1) the anther undergoing normal development which is tetrasporangiate, (2) cytokinesis occurring simultaneously with meiosis in the microspore mother cell, the tetrahedral tetrads, (3) microspores being generated after meiosis by microsporogenesis were more or less irregular in shape during the contraction period. Finally, the abnormal shape and structure of the number of cases reviewed in three replicates of pollens studied can be one of the important factors affecting the decrease in the product.

Embryology and Reproductive Ecology of the Darling Lily, Crinum flaccidum Herbert

In Crinum flaccidum the anthers are versatile and tetrasporangiate with a secretory tapetum of binucleate cells. Successive cytokinesis in microspore mother cell results in isobilateral and decussate microspore tetrads. The mature pollen grains are single, spheroidal, disulculate, echinate and 2-celled. In the mature anthers, fibrous thickenings develop not only in the endothecium but also in two or three middle cell layers and the connective tissue before latrorse dehiscence. A lobed tissue in each of the three locules of the ovary serves ovular and placental functions. Each extension of the 5-7 paired lobes represents an ategmic ovule. The development of the female gametophyte conforms to the Polygonum type. Usually only one gametophyte is present in each lobe but occasionally several may occur. Bulb growth is monopodial with normally three umbels produced per plant, each carrying an average of 10 flowers, only two or three of which are open at any one time. Nectar sugar concentration was measured at 14.2% (w/w), of which 44.8% of solids was sucrose and 3.9% either glucose or fructose. The protandrous flowers are phalenophilous, pollinated by sphingid moths. The endosperm formation is of the nuclear type. In the absence of seed coats and the nucellus at maturity, the outer layers of the endosperm become corky following the activity of a phellogen. Embryogeny appears to be of the Asterad type. The mature embryo is straight and chlorophyllous. The large (5.3 g) seeds are 89% water and show no dormancy, germinating without an external supply of water, sometimes while still on the parent plant.

Microsporogenesis in the normal and male-sterile stamenIess-2 mutant of tomato (Lycopersicon esculentum)

The development of microspores and the associated changes in the tapetum were examined in the normal (+/+) and male-sterile, stamenless-2 (sl-2/sl-2) mutant anthers of tomato (Lycopersicon esculentum). Anthers of eight comparable stages, from the microspore mother cell stage to anthesis, of both lines were processed for light microscopy. Until the formation of tetrads (stage ii), there were no differences in the sporogenous tissue, but the tapetal cells of the mutant were more enlarged than the normal and had, at places, divided to form a bilayer. Later, the tapetal cells in both lines became amoeboid and had sporopollenin-like deposits. At stage iv, whereas the tapetal cells of the normal had started to degenerate, those of the mutant were intact but had large vacuoles. Also at this stage, the deposition of exine was evident in normal microspores, but it was lacking in most mutant microspores, which enlarged considerably and eventually degenerated. From stage v onwards, the normal microspores progressed from the binucleate pollen to pollen containing many vacuoles to mature pollen. In the mutant, tapetum degeneration was delayed until stage v, and later, although some microspores closer to the tapetum appeared normal, most either were empty or had large vacuoles. It is suggested that the delay in tapetum degeneration coupled with the failure of exine deposition, presumably associated with low esterase activity, is responsible for pollen degeneration in the sl-2/sl-2 mutant.

Cytogenetic analysis of interspecific hybrids between alfalfa (Medicago sativa L.) and M. rhodopea Velen.

Interspecific hybrids between diploid (2n = 2x = 16) Medicago sativa L. and diploid (2n = 2x = 16) M. rhodopea Velen., were recovered using an ovule–embryo culture methodology. Most hybrids were vigorous, and morphological comparisons demonstrated that F1 hybrids were generally intermediate between that of the parents. Peroxidase isozyme phenotypes of the F1 hybrids confirmed hybridity. The chromosome number of most of the hybrids was diploid (2n = 2x = 16), with the exceptions of two triploids (2n = 3x = 24) and two tetraploid (2n = 4x = 32) plants. Chromosome pairing configurations in diploids were almost exclusively eight bivalents or seven bivalents and two univalents, indicating a high level of homology between the M. sativa and M. rhodopea genomes. However, the one triploid hybrid analyzed had only 0.4 trivalents per microspore mother cell indicating preferential pairing of parental genomes. Pollen stainability, pollen germination, and fertility of the diploid F1 hybrid plants were very low; however, it was possible to obtain backcross progeny (BC1) from seed. Pollen stainability, pollen germination, and fertility of the BC1 plants were also very low; however, most BC1 plants had workable levels of male and female fertility. The utilization of M. rhodopea in studies of the evolution of hexaploid Medicago species is discussed. Key words: interspecific hybrids, ovule–embryo culture, isozymes, Medicago.

Genetics, cytology, and crossing behavior of an alfalfa (Medicago sativa) mutant resulting in failure of the postmeiotic cytokinesis

During pollen investigations on diploid alfalfa (Medicago sativa L.) several plants were identified which produced "jumbo" pollen. The cause of the jumbo pollen is failure of the postmeiotic cytokinesis. These plants produce a single, four-nucleate microspore from one microspore mother cell (MMC) rather than the normal four, single-nucleate microspores from one MMC. Subsequent gametophyte development is characterized by fusion of the four nuclei into a single nucleus in most cases (range of 80 to 100%), followed by a developmental sequence comparable to normal alfalfa. Mature 4n male gametophytes are thus formed from 2n sporophytes. Genetic control of the postmeiotic cytokinesis failure is by a single recessive gene, designated jp. Although a low frequency of jumbo pollen does germinate (range of 3.1 to 37.8%), crossing studies demonstrate jumbo pollen is incapable of effecting fertilization. The use of the jp mutant in breeding studies, and interspecific hybridization research, is discussed.