Immature Maize Kernels Research Articles

Phenotypic and Proteomic Insights into Differential Cadmium Accumulation in Maize Kernels.

The contamination of agricultural soil with cadmium (Cd), a heavy metal, poses a significant environmental challenge, affecting crop growth, development, and human health. Previous studies have established the pivotal role of the ZmHMA3 gene, a P-type ATPase heavy metal transporter, in determining variable Cd accumulation in maize grains among 513 inbred lines. To decipher the molecular mechanism underlying mutation-induced phenotypic differences mediated by ZmHMA3, we conducted a quantitative tandem mass tag (TMT)-based proteomic analysis of immature maize kernels. This analysis aimed to identify differentially expressed proteins (DEPs) in wild-type B73 and ZmHMA3 null mutant under Cd stress. The findings demonstrated that ZmHMA3 accumulated higher levels of Cd compared to B73 when exposed to varying Cd concentrations in the soil. In comparison to soil with a low Cd concentration, B73 and ZmHMA3 exhibited 75 and 142 DEPs, respectively, with 24 common DEPs shared between them. ZmHMA3 showed a higher induction of upregulated genes related to Cd stress than B73. Amino sugar and nucleotide sugar metabolism was specifically enriched in B73, while phenylpropanoid biosynthesis, nitrogen metabolism, and glyoxylate and dicarboxylate metabolism appeared to play a more significant role in ZmHMA3. This study provides proteomics insights into unraveling the molecular mechanism underlying the differences in Cd accumulation in maize kernels.

Potential roles of WRKY transcription factors in regulating host defense responses during Aspergillus flavus infection of immature maize kernels

The mechanisms regulating the expression of maize resistance genes against Aspergillus flavus are poorly understood. This study examined the potential roles of six WRKY transcription factors and the expression of three pathway indicator genes in response to A. flavus inoculation in B73 (susceptible) and TZAR101 (resistant). The genes ZmWRKY19, ZmWRKY53, and ZmWRKY67 were found to possess elevated expression in TZAR101. ZmNPR1 expression was induced by inoculation in TZAR101 without concurrent induction of ZmPR-1, possibly due to the induction of ZmERF1. These findings indicate that WRKY transcription factors are involved in resistance and that salicylic acid and ethylene signaling may coordinate defense responses.

Gene Expression Profile and Response to Maize Kernels by Aspergillus flavus

Aspergillus flavus causes an ear rot of maize, often resulting in the production of aflatoxin, a potent liver toxin and carcinogen that impacts the health of humans and animals. Many aspects of kernel infection and aflatoxin biosynthesis have been studied but the precise effects of the kernel environment on A. flavus are poorly understood. The goal of this research was to study the fungal response to the kernel environment during colonization. Gene transcription in A. flavus was analyzed by microarrays after growth on kernels of the four developmental stages: blister (R2), milk (R3), dough (R4), and dent (R5). Five days after inoculation, total RNA was isolated from kernels and hybridized to Affymetrix Gene Chip arrays containing probes representing 12,834 A. flavus genes. Statistical comparisons of the expression profile data revealed significant differences that included unique sets of upregulated genes in each kernel stage and six patterns of expression over the four stages. Among the genes expressed in colonized dent kernels were a phytase gene and six putative genes involved in zinc acquisition. Disruption of the phytase gene phy1 resulted in reduced growth on medium containing phytate as the sole source of phosphate. Furthermore, growth of the mutant (Δphy1) was 20% of the wild-type strain when wound inoculated into maize ears. In contrast, no difference was detected in the amount of aflatoxin produced relative to fungal growth, indicating that phy1 does not affect aflatoxin production. The study revealed the genome-wide effects of immature maize kernels on A. flavus and suggest that phytase has a role in pathogenesis.

Phosphorylation of maize and Arabidopsis HMGB proteins by protein kinase CK2alpha.

In plants, a variety of chromatin-associated high mobility group (HMG) proteins belonging to the HMGB family have been identified. We have examined the phosphorylation of the HMGB proteins from the monocotyledonous plant maize and the dicotyledonous plant Arabidopsis by protein kinase CK2alpha. Maize CK2alpha phosphorylates the maize HMGB1 and HMGB2/3 proteins and the Arabidopsis HMGB1, HMGB2/3, and HMGB4 proteins. Maize HMGB4 and HMGB5 and Arabidopsis HMGB5 are not phosphorylated by CK2alpha. Depending on the HMGB protein up to five amino acid residues are phosphorylated in the course of the phosphorylation reaction. The HMGB1 proteins from both plants are markedly more slowly phosphorylated by CK2alpha than the other HMGB substrate proteins, indicating that certain HMGB proteins are clearly preferred substrates for CK2alpha. The rate of the phosphorylation reaction appears to be related to the ease of interaction between CK2alpha and the HMGB proteins, as indicated by chemical cross-linking experiments. MALDI/TOF mass spectrometry analyses demonstrate that the HMGB1 and HMGB2/3 proteins occur in various phosphorylation states in immature maize kernels. Thus, HMGB1 exists as monophosphorylated, double-phosphorylated, triple-phosphorylated, and tetraphosphorylated protein in kernel tissue, and the tetraphosphorylated form is the most abundant version. The observed in vivo phosphorylation states indicate that protein kinase(s) other than CK2alpha contribute(s) to the modification of the plant HMGB proteins. The fact that the HMGB proteins are phosphorylated to various extents reveals that the existence of differentially modified forms increases the number of distinct HMGB protein variants in plant chromatin that may be adapted to certain functions.

Isolation of a Gene Encoding a Glycosylated Cytokinin Oxidase from Maize

The major cytokinin oxidase in immature maize kernels was purified to homogeneity. Selected tryptic peptides were used to design degenerate oligonucleotide primers for PCR isolation of a fragment of the oxidase gene. Hybridization of the PCR fragment to a maize genomic library allowed isolation of a full-length cytokinin oxidase gene (ckx1). The gene encodes a protein of approximately 57 kDa that possesses a signal peptide, eight consensusN-glycosylation sequences and a consensus FAD binding sequence. Expression ofckx1in Pichia caused secretion of active glycosylated cytokinin oxidase that contains a substrate-reducible FAD. The gene displays sequence homology with a putative oxidoreductase fromArabidopsis thalianaand with thefas5gene fromRhodococcus fascians.

Characterization of a barley gene coding for an alpha-amylase inhibitor subunit (CMd protein) and analysis of its promoter in transgenic tobacco plants and in maize kernels by microprojectile bombardment.

A gene coding for a barley CMd protein was isolated from a genomic library using a cDNA probe encoding the wheat CM3 protein. Promoter sequence analysis reveals motifs found in genes specifically expressed in endosperm and aleurone cells, as well as TATA and other putative functional boxes. 720 bp of the Hv85.1 CMd protein gene promoter, when fused to a gus coding region, were unable to direct GUS activity in the seeds of transgenic tobacco plants. In contrast, the same construction delivered into immature maize kernels by microprojectile bombardment was able to direct expression of GUS in the outermost cell layers of maize endosperm in both a tissue-specific and a developmentally determined manner.

Multiple interactions between nuclear proteins of Zea mays and the promoter of the Shrunken gene.

Nuclear proteins were extracted from isolated nuclei of immature maize kernels. The promoter region (1.5 kb) of the Shrunken gene, which is highly transcribed in the developing endosperm of the kernel, was scanned for protein-DNA interactions. Several promoter fragments showed protein-DNA complex formation in gel retardation experiments. Two different nucleo-protein complexes (MNP1 and MNP2) have been distinguished in competition and DNase I footprinting experiments. Both nuclear DNA-binding activities are able to recognize multiple sites distributed over a 1.5 kb upstream region of the Shrunken gene. Some of the binding sites established in the in vitro reconstitution experiments are located near to DNase I hypersensitive sites found in the promoter of the Shrunken gene (Frommer and Starlinger 1988).

Further studies on the auxins of immature maize kernels

AbstractThe separation of the water‐soluble auxins of immature kernels of Zea mays cv. Kelvedon Glory, by column chromatography on silica gel was investigated. The relative growth‐promoting properties of the zeanin YZ fraction in relation to Avena coleoptiles and on cress roots, were investigated. It is suggested that the properties of zeanins could be explained if they were N‐(indole‐3‐acetyl)‐carbamoyl derivatives of carbohydrates.

Investigation of purinelike compounds in immature maize kernels, germinating barley seeds, and yeast

The purinelike compounds in immature maize kernels, germinating barley seeds, and baker's yeast were extracted with ethanol and separated by precipitation with cuprous oxide, chromatography on Dowex I and paper chromatography in n-butanol: acetic acid:water (4:1:5). The purines were located on the paper chromatograms with silver nitrate-bromophenol blue. The ultraviolet spectra of eluates in water and in 0.01 N NaOH were determined. The eluates were also examined for kinetinlike activity by testing their ability to retard the degradation of chlorophyll in the cells of leaf tissue. Nine purinelike compounds were detected in maize, ten in barley, and four in yeast. Guanosine, guanine, adenosine, and adenine were tentatively identified in maize; guanosine, guanine, adenosine, adenine, xanthine, and hypoxanthine in barley; and xanthine, hypoxanthine, and adenine in yeast. Other compounds that showed purinelike ultraviolet spectra could not be identified. The unknown purinelike compounds of R f values of 0.06, 0.75, and 0.81 from maize and 0.06 from barley retarded the breakdown of chlorophyll of wheat or barley leaves floated on their solution. All other compounds from maize, barley or yeast were inactive in this assay. It is suggested that several kinins occur naturally in plants. Since kinetin and naturally occurring kinins were effective in maintaining the detached green leaves turgid and green but were ineffective in preserving the turgidity of the detached albino leaves; therefore, chloroplast are in some way involved in the response of detached leaves to kinins.

The zeanins: a group of growth-promoting compounds from immature maize kernels.

The zeanins: a group of growth-promoting compounds from immature maize kernels.

Auxins in Immature Maize Kernels

ETHER extracts of maize-kernel pulp at pH 6 contain only part of the growth-promoting activity of the kernels. The juice expressed from the ether-extracted kernels is still highly active in the straight-growth test. In Table 1 the activity of the expressed juice from ether-extracted maize kernels is compared with that of an equivalent concentration of ether-extractable material.

The Growth Substances separated from Plant Extracts by Chromatography. I

SUMMARY Methods for the chromatographic separation on paper of indole compounds and for the direct biological assay of the chromatograms using the Avena cole optile straight-growth method are described. Reagents for the detection of the indole-3-carboxylic acids, indole-3-acetonitrile, and gramine as coloured spots on chromatograms are compared and the areas of such spots are shown to be pro portional to the logarithms of the quantities of substance present. The procedure of chromatography described is shown not to involve a loss of indole-3-acetic acid activity if chromatography is done in darkness and chromato grams are not stored in light and air. Methods are described for the extraction of growth substances from plant materials, the purification and chromatography, on paper, of the extracts and the bioassay of the chromatograms using Avena coleoptile sections. The ether extracts, containing acidic substances, of etiolated broad bean and pea shoots and roots, etiolated sunflower shoots, maize roots, and potato etiolated shoots and tuber have been chromatographed and the chromatograms bioassayed. On all chromatograms three areas active in Avena coleoptile section growth are found. One area of growth promotion is shown due to indole-3-acetic acid [IAA], Another area of growth promotion and one of growth inhibition are due to unknown substances, which are named accelerator a (a) and inhibitor (fi) respectively. On chromatograms of potato tuber a fourth growth-promoting area, in addition to those described above, is detected and is shown to be probably due to indole 3-acetonitrile [IAN], IAN or indole-3-pyruvic ac'd may occur together with IAA on chromatograms of extracts of immature maize kernels and cauliflower head respectively. On cabbage extract chromatograms the growth-promoting activity correspond ing in position with IAA is shown to be due to IAA and to IAA alone. In etiolated broad bean shoots IAA is the predominating growth substance in the stem and /3 predominates in the first lateral bud. The latter is suggested as an explanation of apical dominance, and the predominance of j8 in potato tuber skin is suggested as an explanation of dormancy in tubers. In the broad bean root the acidic growth-substance patterns, for the whole root and for the sections 0-2 cm. and 2-4 cm. from the tip, are the same. The acidic growth substances extractable from broad bean shoots are the same whether the plant material is boiled or frozen before extraction.