Lipid-sugar interactions : relevance to anhydrous biology

The ability of seeds and other anhydrous plant forms to survive the withdrawal of water must involve a mechanism for protecting the integrity of cellular membranes. Evidence from animal systems implicates sugars as protective components, and we have tested the changes in mesomorphic phase state of phospholipid model membranes upon hydration and dehydration in the presence of sucrose and/or sucrose plus raffinose. X-ray diffraction studies of dry dimyristoylphosphatidylcholine (DMPC) indicate that the presence of sucrose lowers the chain order/disorder transition temperature to that of hydrated lipid; likewise, the lamellar repeat spacings showed the dry DMPC/sucrose mixture to be similar to that of the hydrated lipid. These results support the proposed potential of sugars to substitute for water in biomembranes. If sucrose is to serve as a protectant during desiccation of seeds, its tendency to crystallize would lessen its effectiveness. Raffinose is known to serve as an inhibitor of sucrose crystallization, and is abundant in seeds. The addition of raffinose to make DMPC/sucrose/raffinose mixtures (1/1/0.3 mass ratio) prevented sucrose crystallization, suggesting this as a possible in vivo role for raffinose.     

Stem cell research: its relevance to reproductive biology

Stem cells provide an excellent model system to understand the differentiation, development and functioning of gonads, and further use of these cells in transplantation or cell-based therapies. Embryonic germ cells present as a better source of pluripotent stem cells. The germ cells are specialized cells, which differentiate into sperm or oocytes. Spermatogonial stem cells are the only stem cells in the adult mammalian body that can be recognized and studied at cellular level with respect to proliferation and differentiation. In the present study, basic process of spermatogenesis, testicular niche and molecular regulation of spermatogenesis and density regulation has been discussed. Research on oogonial stem cells has recently been encouraged due to the demand for oocytes for various research purposes. Mechanism of regulation of follicle formation, oocyte attrition and follicle development and atresia are only partially understood. Hence, the stages of development, its interaction with the neighbouring somatic cells during each developmental stage and the molecular regulation underlying it has been reviewed. These studies will result in establishment of treatment of ovarian disorders, and in identifying cure for infertility that occurs due to ovarian pathophysiology. Indian scenario in terms of stem cell research and its benefits is also discussed.     

Transforming growth factor-beta : biology and clinical relevance

Transforming growth factor-beta is a pleiotropic growth factor that has enthralled many investigators for approximately two decades. In addition to many reports that have clarified the basic mechanism of transforming growth factor-beta signal transduction, numerous laboratories have published on the clinical implication/application of transforming growth factor-beta . To name a few, dysregulation of transforming growth factor-beta signaling plays a role in carcinogenesis, autoimmunity, angiogenesis, and wound healing. In this report, we will review these clinical implications of transforming growth factor-beta .     

Phospholipids in the developing soybean seed

The distribution of phospholipids in developing soybean seeds [Glycine max (L.) Merr., var. “Chippewa 64,” “Harosoy 63,” “Wayne,” and “Clark 63”] was followed. From 30 to 60 days after flowering expressed as mole per cent of phospholipid phosphorus phosphatidic acid decreased from 14.8 to 9.1; phosphatidylinositol increased from 0 to 9.1; phosphatidylcholine increased from 8.2 to 9.8; phosphatidylethanolamine increased from 5.3 to 8.6; phosphatidylglycerol increased from 3.2 to 4.8; diphosphatidylglycerol increased from 2.7 to 4.1; and N-acylphosphatidylethanolamine decreased from 65.8 to 54.6. However, from 60 days after flowering to maturity, phosphatidic acid decreased to 0; phosphatidylinositol increased roughly 2-fold; phosphatidylcholine increased roughly 4.7-fold; phosphatidylethanolamine increased 3-fold; N-acylphosphatidylethanolamine decreased 11-fold; whereas phosphatidylglycerol and diphosphatidylglycerol remained essentially constant. Percentages of individual phospholipid species were not statistically different between any two varieties at a given time period.     

Agrobacterium rhizogenes-mediated transformation of soybean to study root biology

This protocol is used to induce transgenic roots on soybean to study the function of genes required in biological processes of the root. Young seedlings with unfolded cotyledons are infected at the cotyledonary node and/or hypocotyl with Agrobacterium rhizogenes carrying the gene construct to be tested and the infection sites are kept in an environment of high humidity. When the emerged hairy roots can support the plants, the main roots are removed and the transgenic roots can be tested. Using this method, almost 100% of the infected plants form hairy roots within 1 month from the start of the experiments.     

Molecular biology of Rh proteins and relevance to molecular medicine

The Rhesus (Rh) blood group system is expressed by a pair of 12-transmembrane-domain-containing proteins, the RhCcEe and RhD proteins. RhCcEe and RhD associate as a Rh core complex that comprises one RhD/CcEe protein and most likely two Rh-associated glycoproteins (RhAG) as a trimer. All these Rh proteins are homologous and share this homology with two human non-erythroid proteins, RhBG and RhCG. All Rh protein superfamily members share homology and function in a similar manner to the Mep/Amt ammonium transporters, which are highly conserved in bacteria, plants and invertebrates. Significant advances have been made in our understanding of the structure and function of Rh proteins, as well as in the clinical management of Rh haemolytic disease. This review summarises our current knowledge concerning the molecular biology of Rh proteins and their role in transfusion and pregnancy incompatibility.     

The role of kindlins in cell biology and relevance to human disease

The kindlins represent a class of focal adhesion proteins implicated in integrin activation. They comprise three evolutionarily conserved members, kindlin-1, kindlin-2 and kindlin-3, that share considerable sequence and structural similarities. The kindlins have a bipartite FERM (four point one protein, ezrin, radixin, moesin) domain interrupted by a pleckstrin homology domain and can bind directly to various classes of integrins as well as participate in inside–out integrin activation. They are encoded by three different genes, namely KIND1 (FERMT1; chromosome 20p12.3), KIND2 (FERMT2; chromosome 14q22.1) and KIND3 (FERMT3; chromosome 11q13.1). Loss-of-function mutations in KIND1 and KIND3 cause Kindler syndrome and leukocyte adhesion deficiency-III syndrome, respectively, although no human disease has yet been associated with KIND2 gene pathology. In this review, we focus on the cellular functions of the kindlins and their clinical relevance.     

The relevance of seed membrane lipids to imbibitional chilling effects

Imbibitional chilling injury during rehydration of seeds is particularly marked in soybean but not in pea. Following the previous reports that the deleterious effects of chilling on soybean germination are probably mediated at least in part through a loss of membrane integrity, differences in composition of membrane lipid components extracted from pea (chilling-insensitive) and soybean (chilling-sensitive) were examined. Comparative compositional analysis of phospholipids, fatty acids and free sterols revealed few disparities between the two species. When the membrane lipids were re-formed into liposomes, little difference in permeability was found with respect to KCl, glucose or glycerol, even at chilling temperatures. It is suggested that the difference in chilling sensitivity between pea and soybean is not related to compositional differences in the major lipid components of the seed membranes.     

Inheritance of resistance to Phomopsis seed decay in PI 360841 soybean

Phomopsis longicolla Hobbs is the primary cause of Phomopsis seed decay (PSD) in soybean. Infection may result in moldy seed and poor germination. The objective of this study was to conduct inheritance studies to characterize resistance to PSD in plant introduction (PI) 360481. Crosses were made between PI 360841 and 2 PSD-susceptible genotypes, Agripro (AP) 350 and PI 91113, to determine the number of genes for resistance. Additionally, crosses were made between PI 360841 and Phomopsis resistant parents MO/PSD-0259 and PI 80837 to test the allelism of the resistance genes. Seed infection assays were done using seed from parent plants and F(2) populations. Chi-square analysis of the resistant x susceptible F(2) data fit to a 9R:7S model for 2 complementary dominant genes conferring PSD resistance in PI 360841. Segregation for reaction in the F(2) of MO/PSD-0259 x PI 360841 exhibited a good fit to a 57R:7S model for 2 complementary dominant genes from PI 360841 and a different dominant gene from MO/PSD-0259. There was no apparent segregation in the F(2) population from PI 360841 x PI 80837 except for one suspicious susceptible plant, suggesting one of the genes in PI 360841 is the same gene in PI 80837 for PSD resistance.     

An assessment of phase transitions in soybean membranes

Phase transitions were measured in vesicles of phospholipids, alone and in various combinations, and in pelleted mitochondrial membranes, using thermal (DSC) and optical methods. The objective was to consider their possible involvement in chilling injury of soybeans (Glycine max [L.] Merr. cv Wayne 1977). Saturated phospholipids showed clear transitions in the temperature range of 50°C to near 0°C. When mixtures of two phospholipids were examined, there was a marked lowering and broadening of the transition peaks, and a shift in the transition temperatures to intermediate temperatures. The unsaturated phospholipids that occur naturally in soybeans showed no detectable phase transitions in this temperature range, alone or in combinations. Examination of the polar lipids from soybean asolectin revealed no transitions in the biological temperature range; the additions of cations such as Ca²⁺ and La³⁺ did not evoke a detectable phase transition in them. Mitochondrial membrane pellets likewise showed no transitions. The application of these two direct methods of examination of membrane components without the addition of foreign agents did not support the suggested occurrence of a bulk phase transition which could be related to chilling injury in soybeans.     

Control of seed coat thickness and permeability in soybean : a possible adaptation to stress

Although the seed coat, through its thickness and permeability, often regulates seed germination, very little is known about the control of its development. Using soybean (Glycine max [L.] Merrill) explants, podbearing cuttings in which defined solutions can be substituted for the roots, we have demonstrated that cytokinin and mineral nutrients moving through the xylem can control soybean seed coat development. Lack of cytokinin and minerals in the culture solution, causes a thicker, less permeable seed coat to develop. The seeds with thickened coats will imbibe water rapidly if scarified; furthermore, these scratched seeds also germinate and produce normal plants. Inasmuch as stress (e.g. drought) decreases mineral assimilation and cytokinin production by the roots, the resulting delay in germination could be an adaptive response to stress.     

Antigenic relationship of legume seed proteins to the 7S seed storage protein of soybean

Extracts enriched for globulin proteins were prepared from the seeds of a large number of legume species and were tested for homology to antisera prepared against the glycosylated 7S seed storage protein of the soybean (Glycine max). Electrophoretic identification and subsequent analysis of proteins precipitated with 7S antisera was useful at relatively short taxonomic distances, particularly within the tribe Phaseoleae, to which G. max belongs. Glycine and most other members of the subtribe Glycininae are unusual within the Phaseoleae in having high molecular weight ($\text{> 70 000}$ dalton) subunit polypeptides. Seeds from other plants representing other subtribes of the Phaseoleae also contained proteins that cross-reacted with the G. max antisera; the molecular weights of these proteins varied from 30 000 to nearly 90 000 daltons. Homology was detected across a wider range of legume tribes within the subfamily Papilionoideae by enzyme-linked immunosorbent assay (ELISA). The results of these experiments suggest both that the 7S proteins of these tribes are evolutionarily related and that at least some features of these apparently rapidly-evolving proteins are under relatively strong selectional constraint.     

Genetic mapping of resistance to purple seed stain in PI 80837 soybean

Purple seed stain (PSS) of soybean caused by Cercospora kikuchii is an important disease that reduces market grade and can affect seed germination and vigor. A single dominant gene was shown to confer PSS resistance in PI 80837. The objective of this research was to map the PSS resistance gene in PI 80837 using simple sequence repeat (SSR) markers. A cross was made between the PSS-susceptible cultivar Agripro 350 (AP 350) and PI 80837. The F2 population and parents were grown in the field, and the resistance or susceptibility of individual plants was determined by assaying the seed for infection by C. kikuchii. DNA of parent and F2 plants was extracted for SSR analysis and mapping. Segregation ratios for seed infection and for SSR markers showed that a single dominant gene conditions resistance to PSS in PI 80837. The candidate resistance gene was mapped between Sat_308 (6.6 cM) and Satt594 (11.6 cM) on molecular linkage group G. These markers may be useful in marker-assisted selection for utilizing PSS resistance from PI 80837 in a breeding program.     

Hourglass cell development in the soybean seed coat

Background and Aims

Hourglass cells (HGCs) are prominent cells in the soybean seed coat, and have potential use as ‘phytofactories’ to produce specific proteins of interest. Previous studies have shown that HGCs initiate differentiation at about 9 d post-anthesis (dpa), assuming their characteristic morphology by 18 dpa. This study aims to document the structural changes in HGCs during this critical period, and to relate these changes to the concurrent development of a specific soybean peroxidase (SBP) encoded by the Ep gene.

Methods

Pods were collected from plants at specific growth stages. Fresh material was processed for analysis of Ep peroxidase activity. Tissues were processed for scanning and transmission electron microscopy, as well as extracted for western blotting. A null variety lacking expression of Ep peroxidase was grown as a control.

Key Results and Conclusions

At 9 dpa, HGCs are typical undifferentiated plant cells, but from 12–18 dpa they undergo rapid changes in their internal and external structure. By 18 dpa, they have assumed the characteristic hourglass shape with thick cell walls, intercellular air spaces and large central vacuoles. By 45 dpa, all organelles in HGCs have been degraded. Additional observations indicate that plasmodesmata connect all cell types. SBP activity and SBP protein are detectable in the HGC before they are fully differentiated (approx. 18 dpa). In very early stages, SBP activity appears localized in a vacuole as previously predicted. These results increase our understanding of the structure and development of the HGC and will be valuable for future studies aimed at protein targeting to components of the HGC endomembrane systems.     

Special secretory cells in the soybean seed coat

Summary The seed coat of soybean (Glycine max L. Merr.) is of physiological interest for synthesis and transport of amino acids and photosynthates during embryo development. A transmission and scanning electron microscopic study to elucidate the structure of the seed coat disclosed a specialized convex area (antipit) appressed to a concave pit in the center of the abaxial surface of the cotyledon. The antipit, which lies on the inner surface of the seed coat at a medial point in the anterior to posterior direction of the seed, contained specialized secretory cells bounded by loose multi-layered cell walls. These cells were rectangular in the developing seed, varied in length, and contributed directly to the convex morphology of the antipit seen on the ventral surface of the seed coat. At maturity these cells assumed the shape of a cone, extending from the aleurone layer in a perpendicular array. The aleurone and cone cells contained numerous Golgi apparatus, laminated rough endoplasmic reticulum, secretory vesicles, and amyloplasts. Secretory vesicles arose directly from tubules of fenestrated trans cisternae of the Golgi apparatus. Mitochondria were clustered with the amyloplasts; stacks of lamellar cisternae of rough endoplasmic reticulum were associated with the nucleus and Golgi apparatus. The cellular contents, the interconnections by plasmodesmata, and the close physical association with the cotyledon suggested that the aleurone and cone cells may be involved in symplastic transport of nutrients for use by the developing embryo.This paper is dedicated to the memory of my parents, Joseph and Theresa Yaklich, who by their example taught me the value of work and the enjoyment of simple things.     

立地条件和树龄对刺槐和小叶杨叶水力性状及抗旱性的影响

以形成黄土高原“小老树”的2种典型树种刺槐和小叶杨为对象,研究了立地条件(沟谷台地和沟间坡地)和树龄对两种树木叶水力学性质和抗旱性的影响,探讨“小老树”形成的水力生理机制.结果表明: 水分较好的沟谷台地上生长的两种树木的叶最大水力导度(K_max)明显大于水分较差的沟间坡地,叶水力脆弱性(P₅₀)也较高;随树龄增加,两种树木的K_max明显下降,但P₅₀差异不大.台地上生长的两种树木的叶表皮导度和PV曲线参数(膨压损失点时的相对含水量RWC_tlp、膨压损失点时的水势ψ_tlp、饱和含水量时的渗透势ψ_sat)均大于坡地;随树龄增加,两种树木的叶表皮导度显著下降,PV曲线参数出现不同程度的下降.两种树木K_max与ψ_tlp呈显著正相关,P₅₀与PV曲线参数之间存在一定的相关性,表明K_max与抗旱性之间存在一种权衡关系,P₅₀是反映两种树木的抗旱性特征之一.