Research Notes : Isolation of soybean lectin specific polysomes by immunoadsorption

Soybean lectin (SBL), a glycoprotein found in seeds, is capable of agglutinating red blood cells. SBL has a molecular weight of 120,000 daltons and is composed of four subunits of 30,000 daltons (Lis and Sharon, 1973). SBL protein comprises 0.5-5% of the total protein in defatted meal, depending upon the soybean variety used (Pull et al., 1978)

Specific elements of the glyoxylate pathway play a significant role in the functional transition of the soybean cotyledon during seedling development

Abstract Background The soybean (Glycine max) cotyledon is a specialized tissue whose main function is to serve as a nutrient reserve that supplies the needs of the young plant throughout seedling development. During this process the cotyledons experience a functional transition to a mainly photosynthetic tissue. To identify at the genetic level the specific active elements that participate in the natural transition of the cotyledon from storage to photosynthetic activity, we studied the transcript abundance profile at different time points using a new soybean oligonucleotide chip containing 19,200 probes (70-mer long). Results After normalization and statistical analysis we determined that 3,594 genes presented a statistically significant altered expression in relation to the imbibed seed in at least one of the time points defined for the study. Detailed analysis of this data identified individual, specific elements of the glyoxylate pathway that play a fundamental role during the functional transition of the cotyledon from nutrient storage to photosynthesis. The dynamics between glyoxysomes and peroxisomes is evident during these series of events. We also identified several other genes whose products could participate co-ordinately throughout the functional transition and the associated mechanisms of control and regulation and we described multiple unknown genetic elements that by association have the potential to make a major contribution to this biological process. Conclusion We demonstrate that the global transcript profile of the soybean cotyledon during seedling development is extremely active, highly regulated and dynamic. We defined the expression profiles of individual gene family members, enzymatic isoforms and protein subunits and classified them accordingly to their involvement in different functional activities relevant to seedling development and the cotyledonary functional transition in soybean, especially the ones associated with the glyoxylate cycle. Our data suggests that in the soybean cotyledon a very complex and synchronized system of control and regulation of several metabolic pathways is essential to carry out the necessary functions during this developmental process.</p

Research Notes : United States : Analysis of active transposable element systems in soybean

Since the identification of an insertion element (Tgml) in the lectin gene (Lel) of lectin-negative soybean lines (Goldberg et al., 1983; Vodkin et al., 1983), this laboratory has been interested in identifying and characterizing active transposable element systems of soybean. Tgml exhibits the structural features of known transposable element and appears to be related to the En/Spm elements of corn and Taml of snapdragon (Rhodes and Vodkin, 1985). However, there is no evidence for mobility of Tgml and the Le-phenotype is stably inherited

Flux of transcript patterns during soybean seed development

<p>Abstract</p> <p>Background</p> <p>To understand gene expression networks leading to functional properties of the soybean seed, we have undertaken a detailed examination of soybean seed development during the stages of major accumulation of oils, proteins, and starches, as well as the desiccating and mature stages, using microarrays consisting of up to 27,000 soybean cDNAs. A subset of these genes on a highly-repetitive 70-mer oligonucleotide microarray was also used to support the results.</p> <p>Results</p> <p>It was discovered that genes related to cell growth and maintenance processes, as well as energy processes like photosynthesis, decreased in expression levels as the cotyledons approached the mature, dry stage. Genes involved with some storage proteins had their highest expression levels at the stage of highest fresh weight. However, genes encoding many transcription factors and DNA binding proteins showed higher expression levels in the desiccating and dry seeds than in most of the green stages.</p> <p>Conclusions</p> <p>Data on 27,000 cDNAs have been obtained over five stages of soybean development, including the stages of major accumulation of agronomically-important products, using two different types of microarrays. Of particular interest are the genes found to peak in expression at the desiccating and dry seed stages, such as those annotated as transcription factors, which may indicate the preparation of pathways that will be needed later in the early stages of imbibition and germination.</p

Transcriptome changes in the phenylpropanoid pathway of Glycine max in response to Pseudomonas syringae infection

BACKGROUND: Reports of plant molecular responses to pathogenic infections have pinpointed increases in activity of several genes of the phenylpropanoid pathway leading to the synthesis of lignin and flavonoids. The majority of those findings were derived from single gene studies and more recently from several global gene expression analyses. We undertook a global transcriptional analysis focused on the response of genes of the multiple branches of the phenylpropanoid pathway to infection by the Pseudomonas syringae pv. glycinea with or without the avirulence gene avrB to characterize more broadly the contribution of the multiple branches of the pathway to the resistance response in soybean. Transcript abundance in leaves was determined from analysis of soybean cDNA microarray data and hybridizations to RNA blots with specific gene probes. RESULTS: The majority of the genes surveyed presented patterns of increased transcript accumulation. Some increased rapidly, 2 and 4 hours after inoculation, while others started to accumulate slowly by 8 – 12 hours. In contrast, transcripts of a few genes decreased in abundance 2 hours post inoculation. Most interestingly was the opposite temporal fluctuation in transcript abundance between early responsive genes in defense (CHS and IFS1) and F3H, the gene encoding a pivotal enzyme in the synthesis of anthocyanins, proanthocyanidins and flavonols. F3H transcripts decreased rapidly 2 hours post inoculation and increased during periods when CHS and IFS transcripts decreased. It was also determined that all but one (CHS4) family member genes (CHS1, CHS2, CHS3, CHS5, CHS6 and CHS7/8) accumulated higher transcript levels during the defense response provoked by the avirulent pathogen challenge. CONCLUSION: Based on the mRNA profiles, these results show the strong bias that soybean has towards increasing the synthesis of isoflavonoid phytoalexins concomitant with the down regulation of genes required for the synthesis of anthocyanins and proanthocyanins. Although proanthocyanins are known to be toxic compounds, the cells in the soybean leaves seem to be programmed to prioritize the synthesis and accumulation of isoflavonoid and pterocarpan phytoalexins during the resistance response. It was known that CHS transcripts accumulate in great abundance rapidly after inoculation of the soybean plants but our results have demonstrated that all but one (CHS4) member of the gene family member genes accumulated higher transcript levels during the defense response

Microarray analysis of iron deficiency chlorosis in near-isogenic soybean lines

BACKGROUND: Iron is one of fourteen mineral elements required for proper plant growth and development of soybean (Glycine max L. Merr.). Soybeans grown on calcareous soils, which are prevalent in the upper Midwest of the United States, often exhibit symptoms indicative of iron deficiency chlorosis (IDC). Yield loss has a positive linear correlation with increasing severity of chlorotic symptoms. As soybean is an important agronomic crop, it is essential to understand the genetics and physiology of traits affecting plant yield. Soybean cultivars vary greatly in their ability to respond successfully to iron deficiency stress. Microarray analyses permit the identification of genes and physiological processes involved in soybean's response to iron stress. RESULTS: RNA isolated from the roots of two near isogenic lines, which differ in iron efficiency, PI 548533 (Clark; iron efficient) and PI 547430 (IsoClark; iron inefficient), were compared on a spotted microarray slide containing 9,728 cDNAs from root specific EST libraries. A comparison of RNA transcripts isolated from plants grown under iron limiting hydroponic conditions for two weeks revealed 43 genes as differentially expressed. A single linkage clustering analysis of these 43 genes showed 57% of them possessed high sequence similarity to known stress induced genes. A control experiment comparing plants grown under adequate iron hydroponic conditions showed no differences in gene expression between the two near isogenic lines. Expression levels of a subset of the differentially expressed genes were also compared by real time reverse transcriptase PCR (RT-PCR). The RT-PCR experiments confirmed differential expression between the iron efficient and iron inefficient plants for 9 of 10 randomly chosen genes examined. To gain further insight into the iron physiological status of the plants, the root iron reductase activity was measured in both iron efficient and inefficient genotypes for plants grown under iron sufficient and iron limited conditions. Iron inefficient plants failed to respond to decreased iron availability with increased activity of Fe reductase. CONCLUSION: These experiments have identified genes involved in the soybean iron deficiency chlorosis response under iron deficient conditions. Single linkage cluster analysis suggests iron limited soybeans mount a general stress response as well as a specialized iron deficiency stress response. Root membrane bound reductase capacity is often correlated with iron efficiency. Under iron-limited conditions, the iron efficient plant had high root bound membrane reductase capacity while the iron inefficient plants reductase levels remained low, further limiting iron uptake through the root. Many of the genes up-regulated in the iron inefficient NIL are involved in known stress induced pathways. The most striking response of the iron inefficient genotype to iron deficiency stress was the induction of a profusion of signaling and regulatory genes, presumably in an attempt to establish and maintain cellular homeostasis. Genes were up-regulated that point toward an increased transport of molecules through membranes. Genes associated with reactive oxidative species and an ROS-defensive enzyme were also induced. The up-regulation of genes involved in DNA repair and RNA stability reflect the inhospitable cellular environment resulting from iron deficiency stress. Other genes were induced that are involved in protein and lipid catabolism; perhaps as an effort to maintain carbon flow and scavenge energy. The under-expression of a key glycolitic gene may result in the iron-inefficient genotype being energetically challenged to maintain a stable cellular environment. These experiments have identified candidate genes and processes for further experimentation to increase our understanding of soybeans' response to iron deficiency stress