Infected Maize Plants Research Articles

Mutational analysis of the small intergenic region of maize streak virus

Maize streak virus (MSV) is a leafhopper-transmitted geminivirus containing one molecule of circular single-stranded DNA of about 2.7 kb. We have tested the infectivity of MSV mutants. A deletion of 29 bases in the small intergenic region (SIR) did not affect the infectivity of MSV. Mutants containing insertions of oligonucleotides of up to 32 bases at the Asn; site in SIR were also infectious. However, the infection efficiency of these insertion mutants decreased as the size of the olignnucleotides increased. This reduced virulence may be due to a decreased efficiency of 3′-end formation of the complemetary sense mRNA(s). The stability of MSV mutants in infected maize plants was analyzed by polymerase chain reaction (PCR). Some oligonucleotide-insertion mutants were completely stable while others obtained deletions. Infectivity of the mutants, however did not require deletion formation. Deletion rearrangement was shown to be the dependent on the sequence of the inserted oligonucleotide. The AsnI site is the only site known to permit insertion of nonviral DNA without abolishing MSV infectivity. The system described may a delivery vector to introduce at least small segments of DNA into maize.

Point substitutions in a promoter-like region and the V1 gene affect the host range and symptoms of maize streak virus

The nucleotide sequences of full-length infectious clones of two symptomatic and host range variants (MSV-Ns and MSV-Nm) of the Nigerian strain of maize streak virus (MSV) have been determined and shown to differ by only three nucleotides. MSV-Ns produced symptoms in infected maize plants sooner and the streaks were wider and more chlorotic than those of MSV-Nm; variant MSV-Ns also had a wider host range within the Gramineae. None of the three nucleotide differences resulted in amino acid changes. Site-directed mutagenesis showed that a substitution at nucleotide (nt) 40 in the V1 gene affected streak width, while severity of chlorosis, length of streaks, latency, and host range was determined by a single base change at nt 2473 in the large intergenic region. The nt 2473 change altered a potential promoter sequence (TATA box) in MSV-Ns 101 nucleotides upstream of the initiation codon of the C1 gene. Mutagenesis of TATA sequences located downstream of TATA -101 showed that TATA -101 alone was sufficient to confer a wide host range phenotype on MSV-Ns and suggested that it might function as a promoter for the expression of complementary-sense open reading frames. When compared with an updated promoter consensus derived from genes of the Gramineae, the promoter context around TATA -101 in MSV-Ns was not more favorable than those found at -57 and -62 in MSV-Nm.

Characterization of Maize Chlorotic Mottle Virus

Maize chlorotic mottle virus (MCMV) is an icosahedral plant virus 30 nm in diameter, composed of a single 25-kDa capsid protein subunit and a 4.4-kb single-stranded, positive-sense genomic RNA. The genomic RNA is capped at the 5'terminus with m 7 GpppA, and no genome-linked protein was detected. MCMV infection produces two discrete double-stranded RNA species in infected maize plants, corresponding to single-stranded RNAs of 4.4 and 1.1 kb (...)

Vorkommen vonFusarium-Arten und ihren Mykotoxinen auf Silomais

The formation of deoxynivalenol in a maize plot inoculated with Fusarium culmorum was studied over a growing season. Already three weeks after inoculation 4.9 mg/kg of DON were measured in the infected ears. The toxin concentration increased continuously up to harvest after eight weeks to a value of 261 mg/kg. Ensilage experiments in laboratory scale silos have shown that the DON content of naturally contaminated corn-cob-mix was not reduced during the ensilage process. It was concluded that infection of maize plants by toxin-producing Fusarium species followed by DON production in the field seems to be the most probable way of contamination of maize silage with this mycotoxin.

Detection of a non-structural protein of M r 11 000 encoded by the virion DNA of maize streak virus

A polypeptide of approximately 11 000 daltons (11 kDa protein) encoded by an open reading frame (10.9 ORF) from the virion sense of maize streak virus (MSV) DNA has been detected among the products of in vitro translation reactions programmed with RNA from infected maize plants and also in total protein extracts from infected leaves. The 11 kDa protein has not been detected in virions and is therefore proposed to have a nonstructural role.Viral DNA with an additional in-frame translation stop codon in the 10.9 ORF was not infectious when transmitted to maize plants via Agrobacterium tumefaciens "agroinfection", suggesting that the 10.9 ORF may be essential for virus function. Computer comparison data show that equivalent ORFs in wheat dwarf virus (WDV) and digitaria streak virus (DSV) have some sequences in common with the 10.9 ORF of MSV. Further-more, the absence of similar sequences in geminiviruses which infect dicotyledonous plants suggests that the 11 kDa protein and its putative homologs in WDV and DSV have a function necessary only for those geminiviruses which infect the Gramineae.The significance of the 11 kDa protein in relation to expression of the virion sense DNA of MSV is discussed.

The transformation of Zea mays seedlings with Agrobacterium tumefaciens

Virulent strains of the soil bacterium Agrobacterium tumefaciens infect dicotyledonous plants and elicit a profound neoplastic response which results in crown gall formation (18). The inciting agent has been shown to be a high molecular weight plasmid (Ti) a section of which, the T-DNA, integrates into the host plant's genome (4, 28, 30). Although transformation of this kind was presumed to be limited to dicots, the detection of enzyme activities linked to the expression of T-DNA has been demonstrated in monocots from the families Liliaceae and Amaryllidaceae (10, 11).In this communication, we present evidence that a member of the commercially important Gramineae also is subject to A. tumefaciens directed transformation. This conclusion is based on two observations. First, seedlings of Zea mays that have had the bacteria introduced into wound sites defined by a region which includes the scutellar node and mesocotyl express the activity of enzymes whose synthesis is associated with the translation of T-DNA transcripts. Specifically, strain specific lysopine dehydrogenase activity has been detected in B6 infected material, whereas nopaline dehydrogenase activity is reported only in those plants inoculated with C58N. Second, the detection of either of these activities in extracts made from infected maize plants requires that the assaulting bacterial strain be competent with respect to the transfer of T-DNA. The vir (-) strains, JK195 and 238MX, are not, and transformation does not seem to occur. In this connection, the corresponding opine synthase activities are not observed.

Accumulation of Asparagine in Maize Plants infected by Maize Rough Dwarf Virus and its Significance in Plant Virology

IT has already been shown that the rough dwarf disease of maize, so far known only from Italy, Spain and Israel, is caused by a virus1. Since this virus has a pronounced dwarfing effect on maize seedlings, which in most cases proves lethal, it would be expected that certain physiological abnormalities could be determined at a rather early stage of infection. The effect of this virus on the balance of free amino-acids in infected maize plants is being studied in our laboratory. During the course of this work an abnormal accumulation of asparagine was noticed in all plants bearing the virus infection symptoms, whereas in all healthy plants of the same age this amide was at the most only faintly detectable by the method of two-dimensional paper chromatography which we used2. Moreover, when l-asparagine was added to the sap extracted from diseased plants and chromatographed, its spot coincided with the one suspected to be that amide.

Agglutination Test Applied to Strains of Phytomonas stewarti

1. The agglutination test was used in an attempt to identify ninety single-colony isolates of Phytomonas stewarti which were obtained from twenty-seven naturally infected maize plants at Princeton, New Jersey. Three of the isolates failed to agglutinate in either of two sera used, some agglutinated in one or the other but not in both, and the remainder agglutinated in both sera at dilutions of 1:20 to 1:2560. There was no consistent difference in the serological properties of isolates from susceptible and resistant inbred lines of corn. Some isolates from the same leaf lesion were as different from one another as were those from different plants. 2. Strains derived from the same culture were found to differ in their serological characteristics. A study of fifteen strains showed that the serological properties were not correlated with any particular colony characteristic, physiological ability, or degree of virulence. Strains from different localities in the United States and Mexico were no more different from one another than some of the variants derived from one of the strains. Some strains agglutinated in all sera at titers as high as 1:1280 to 1:5120. These strongly agglutinating strains usually induced immune sera that failed to agglutinate five of the strains. The strains that agglutinated poorly, on the other hand, produced sera that were effective against all the cultures tested. 3. Several other species of wilt-producing bacteria did not agglutinate in antiserum for three strains of P. stewarti.