De novo Transcriptome Reveals Gene Changes in the Development of the Endosperm Chalazal Haustorium in Taxillus chinensis (DC.) Danser

Loranthus (Taxillus chinensis) is a facultative, hemiparasite and stem parasitic plant that attacks other plants for living. Transcriptome sequencing and bioinformatics analysis were applied in this study to identify the gene expression profiles of fresh seeds (CK), baby (FB), and adult haustoria tissues (FD). We assembled 160,571 loranthus genes, of which 64,926, 35,417, and 47,249 were aligned to NR, GO, and KEGG pathway databases, respectively. We identified 14,295, 15,921, and 16,402 genes in CK, FB, and FD, respectively. We next identified 5,480 differentially expressed genes (DEGs) in the process, of which 258, 174, 81, and 94 were encoding ribosomal proteins (RP), transcription factors (TF), ubiquitin, and disease resistance proteins, respectively. Some DEGs were identified to be upregulated along with the haustoria development (e.g., 68 RP and 26 ubiquitin genes). Notably, 36 RP DEGs peak at FB; 10 ER, 5 WRKY, 6 bHLH, and 4 MYB TF genes upregulated only in FD. Further, we identified 4 out of 32 microRNA genes dysregulated in the loranthus haustoria development. This is the first haustoria transcriptome of loranthus, and our findings will improve our understanding of the molecular mechanism of haustoria.

Some aspects of embryology of the Poacynum armenum (Apocynaceae)

The article presents some aspects of Poacynum armenum (Pobed.) Mavrodiev, Laktionov et Yu.E .Alexeev embryology. The processes of the male and female generative structures, endosperm formation have been described. Plant material was collected in the area of Cape Sarych on the Southern Coast of the Crimea during flowering and fruiting Poacynum armenum . It has been established that the type of microsporangium wall formation is centrifugal, the formation of microspores tetrads is simultaneous, the mature pollen is 3-cell with a three-furrow shell, the ovule is anatropic, unitegmal, tenuinucellate. Endosperm is cellular with chalazal haustorium. It is shown that one of the reasons for low seed productivity can be significant deviations in the development of male gametophytes and gametes, as well as the absence of pollinating insects during the flowering period. The activity of the sea and anthropogenic impact also have a negative effect, as well as the absence of pollinating insects during the flowering period. However, the formation of full seeds, the presence in this coenopopulation along with generative individuals of seedlings and juvenile individuals indicate seed reproduction of the species and the possibility of its natural renewa

Storage sites in seeds of Caesalpinia echinata and C. ferrea (Leguminosae) with considerations on nutrients flow

The seeds of Caesalpinia echinata and C. ferrea behaved as typical endospermic seeds, despite their different morphological classification (exendospermic seeds were described for C. echinata and endospermic seeds for C. ferrea). Then, the aim of this work was to compare, under ultrastructural and histochemical terms, the nature of the storage substances and their accumulation sites, as well as the nutrient flow in seeds of these species. Cotyledons in C. echinata accumulate carbohydrates, lipids and proteins, which are mobilized from the outer to the inner parts as revealed by the position of plasmodesmata. Endosperm in C. ferrea accumulates carbohydrates and in C. echinata accumulates substances during the initial embryogenic phases. Such tissue develops a chalazal haustorium that is responsible for the transport of substances into the endosperm itself and from it into the embryo, confirmed by the presence of transference cells.

The polytenic endosperm haustorium of Rhinanthus minor (Scrophulariaceae): functional ultrastructure

The seed of Rhinanthus undergoes an uncommon differentiation in developing both a chalazal and a micropylar endosperm haustorium. The chalazal haustorium is described at the ultrastructural level. It shows two giant nuclei with polytene chromosomes and numerous complex nucleoli. The nuclear surface is highly interdigitated with the cytoplasm and displays many pores. The cell wall of the apical region of the haustorium displays a prominent wall labyrinth. A large number of mitochondria are located in this region, while leucoplasts are mainly found in vicinity of the nuclei. The structural features of the haustorium are discussed in relation to its expected functions, i.e., synthetic activity and transfer of nutritive material from surrounding tissues to the endosperm proper. Key words: endosperm, haustorium, polyteny, Rhinanthus, transfer cell.

DEVELOPMENT OF THE SEED AND FRUIT IN MELAMPYRUM NEMOROSUM L. AND M. ARVENSE L.

The ovary is bilocular, with four massive axile placentae, each bearing a sessile hemianatropous, unitegmic, and tenuinucellate ovule. The innermost integumentary layer forms endothelium around the micropylar part of the embryo sac. The micropylar canal is surrounded by the micropylar tube, whereas the endothelium is hypodermal in this region. The endothelium and an adjacent meristematic region contribute to the growth of the integument. The endosperm is of the Brunella type described by K. Schnarf in 1929. The chalazal haustorium is a highly aggressive, two-nucleate chamber which becomes inactive and is filled with a haustorial chalazal endosperm. The two multinucleate micropylar haustorial cells give rise to many tubular extensions which pass through the micropylar tube, but only one reaches the placenta. The cells of the storage endosperm are pitted and thickened with hemicellulose. An opaque tanniferous zone of endosperm separates the storage endosperm from the chalazal endosperm. The embryo is small and straight, with two cotyledons and a hypocotyledonary region. The seed coat is feeble, one to three layered. The pericarp is many layered and cuticularized. The two innermost lignified layers form columns at the dorsal line of the two valves of the capsule, where it dehisces. The chalazal part of the developing seed absorbs nourishment directly from the pericarp.

EMBRYOLOGICAL STUDIES IN CANADIAN REPRESENTATIVES OF THE TRIBE RHINANTHEAE, SCROPHULARIACEAE

Descriptions are given of the ovary and ovules, megasporogenesis, embryo sac, endosperm, embryo, and seed coat structure of Euphrasia arctica Lange, Orthocarpus luteus Nutt., and Melampyrum lineare Desr. Although the ovary is usually bicarpellary, syncarpous, and bilocular with axile placentation in the tribe, a tendency toward unilocularity and parietal placentation occurs in Orthocarpus luteus. The number of ovules is reduced to four in Melampyrum lineare. Development of the embryo sac is of the monosporic eight-nucleate type in Euphrasia arctica and Orthocarpus luteus, but is tetrasporic and seven-nucleate in Melampyrum lineare. No fusion of polar nuclei occurs in the latter. The endosperm is ab initio cellular. Nuclear division in the primary micropylar chamber is followed by a vertical wall which remains incomplete. Aggressive haustoria develop at opposite ends of the endosperm. The chalazal haustorium is unicellular and binucleate. The micropylar haustorium is incompletely bicelled, with four nuclei in E. arctica and M. lineare and two nuclei in O. luteus. In M. lineare six to eight tube-like processes develop from the micropylar haustorium of which one usually enlarges and enters the funicle. The endosperm proper is generally uniform in E. arctica and O. luteus, but in M. lineare it becomes differentiated into three regions, the massive micropylar part consisting of cells with thickened, prominently pitted walls and the chalazal part of thin-walled cells with large intercellular spaces. Embryo development in E. arctica and O. luteus resembles that of Capsella bursa-pastoris, while development in M. lineare follows that of Polygonum persicaria. Embryologically Melampyrum lineare differs markedly from other members of the tribe.