Wheat Primary Roots Research Articles

Comparative Proteomic Analysis Provides Insights into the Regulatory Mechanisms of Wheat Primary Root Growth

Plant roots are vital for acquiring nutrients and water from soil. However, the mechanisms regulating root growth in hexaploid wheat remain to be elucidated. Here, an integrated comparative proteome study on the roots of two varieties and their descendants with contrasting root phenotypes was performed. A total of 80 differentially expressed proteins (DEPs) associated with the regulation of primary root growth were identified, including two plant steroid biosynthesis related proteins and nine class III peroxidases. Real-time PCR analysis showed that brassinosteroid (BR) biosynthesis pathway was significantly elevated in long-root plants compared with those short-root plants. Moreover, O2.− and H2O2 were distributed abundantly in both the root meristematic and elongation zones of long root plants, but only in the meristematic zone of short-root plants. The differential distribution of reactive oxygen species (ROS) in the root tips of different genotypes may be caused by the differential expression of peroxidases. Taken together, our results suggest that the regulation of wheat primary root growth is closely related to BR biosynthesis pathway and BR-mediated ROS distribution.

Architectural traits in response to salinity of wheat primary roots

This article provides a study on morphological and anatomical changes during post-embryonic development of roots in plants under saline stress. The influence of salinity on the architecture of root related to the species-specificity of wheat plants is shown. The important roles of thickness of the epiblema and length of root hairs, the thickness of the endoderm and the diameter of the central cylinder under salt stress appear worthy of note. It is shown that both the water content of roots cells and its chromosomal apparatus are affected by salt stress. In addition to a very strong plasmolysis, the compression and fragmentation of the nuclei were noted, which resulted into their destruction and cell death. On the basis of all considered parameters the studied species can be arranged in the following according their resistance to salinity: T. polonicum < T. compactum < T. aestivum < T. dicoccum. This is confirmed by the data of ion balance of Na+, K+, and Ca2+ in primary roots of different wheat species.

Comparative Proteomic Analysis Provides New Insights Into Low Nitrogen-Promoted Primary Root Growth in Hexaploid Wheat.

Nitrogen deficient environments can promote wheat primary root growth (PRG) that allows for nitrogen uptake in deep soil. However, the mechanisms of low nitrogen-promoted root growth remain largely unknown. Here, an integrated comparative proteome study using iTRAQ analysis on the roots of two wheat varieties and their descendants with contrasting response to low nitrogen (LN) stress was performed under control (CK) and LN conditions. In total, 84 differentially abundant proteins (DAPs) specifically involved in the process of LN-promoted PRG were identified and 11 pathways were significantly enriched. The Glutathione metabolism, endocytosis, lipid metabolism, and phenylpropanoid biosynthesis pathways may play crucial roles in the regulation of LN-promoted PRG. We also identified 59 DAPs involved in the common response to LN stress in different genetic backgrounds. The common responsive DAPs to LN stress were mainly involved in nitrogen uptake, transportation and remobilization, and LN stress tolerance. Taken together, our results provide new insights into the metabolic and molecular changes taking place in contrasting varieties under LN conditions, which provide useful information for the genetic improvement of root traits and nitrogen use efficiency in wheat.

Spatial responses of antioxidative system to aluminum stress in roots of wheat (Triticum aestivum L.) plants

Aluminum (Al) toxicity associated with acid soils represents one of the biggest limitations to crop production worldwide. The root apex of plants is the major perception site of Al toxicity. In Al stressed wheat primary roots, Al accumulation and loss of plasma membrane integrity were highest in the root apex (0–5mm), and decreased along the root axis (5–25mm). To further understand these responses in wheat, spatial profiles of antioxidant responses to Al along the 0–25mm root tip of two wheat genotypes differing in Al tolerance were analyzed. Under Al stress, the lowest root elongation was in the 0–5mm root tip, and more severe inhibition was observed in Al-sensitive genotype than Al-tolerant genotype. The highest increase of Al and hydrogen peroxide (H2O2) was in the 0–5mm zone, with the most pronounced increase of malondialdehyde content and Evans blue uptake after Al exposure, especially in Al-sensitive genotype. The activities of superoxides dismutase (SOD), ascrobate peroxidase (APX), catalase (CAT) and peroxidase (POD) and levels of antioxidants (ascorbic acid, reduced glutathione, dehydroascorbate, glutathione disulfide) were significantly increased along the root tip under Al stress, with the 0–5mm region again being the most active zone. In the same zone, the activities of CAT, APX and contents of antioxidants were higher in Al-tolerant genotype while SOD and POD activities were lower. Our results indicate that Al-induced changes in H2O2 production and antioxidative system in root tip are regulated in a spatially-specific manner, suggesting that this response may play an important role in wheat adaptation to Al toxicity.

Alterations in the proteome of wheat primary roots after wortmannin application during seed germination

Wortmannin is an efficient inhibitor of phosphatidylinositol 3-kinases that is involved in normal plant growth. In this study, we performed the global proteomic analysis of the effects of wortmannin on wheat primary roots during seed germination. Wortmannin significantly inhibited the growth of wheat primary roots in a macroscopic level, and damaged the fine structure of nucleoli and mitochondria in a microscopic level. In total, 75 differentially accumulated protein (DAP) spots representing 66 unique DAPs were identified by linear two-dimensional electrophoresis and tandem mass spectrometry. These DAPs were mainly related to detoxification and defense response, carbon metabolism, and amino acid metabolism. Principal component analysis indicated that wortmannin significantly induced the proteomic changes between the treatment and control groups. Protein–protein interaction analysis revealed a complex network centralized by the 14-3-3 protein which was significantly upregulated in both transcriptional and translational levels. Furthermore, some key DAPs, such as heat shock-related proteins, glyceraldehyde-3-phosphate dehydrogenase, isocitrate dehydrogenase, 5-methyltetrahydropteroyltriglutamate–homocysteine methyltransferase, and elongation factor, also showed significantly upregulated accumulation, indicating their key roles in cell homeostasis maintenance, energy supply, and protein biosynthesis. Results obtained from this study provided a new insight into the molecular mechanism of wheat primary root in response to wortmannin during seed germination.

Chromosomal rearrangements caused by gamma-irradiation in winter wheat cells

In this article we report the results of our investigation into several cytogenetic parameters of variability in mutation induction of modern winter wheat varieties and some connections between the means of cytogenetic indices and different doses of gamma-rays. Analysis of chromosomal aberrations following the action of any kind of mutagen by the anaphases method is one of the most widely investigated and most precise methods which can be used to determine the fact of mutagenic action on plants and identify the nature of the mutagen. We combined in our investigation the sensitivity of genotype to mutagen using cytological analysis of mutagen treated wheat populations with the corresponding different varieties by breeding methods to reveal its connections and differences, specific sensitivity to mutagens action on the cell level. Dry seeds of 8 varieties of winter wheat were subjected to 100, 150, 200, 250 Gy gamma irradiation, which are trivial for winter wheat mutation breeding. We investigated rates and spectra of chromosomal aberrations in the cells of winter wheat primary roots tips. The coefficients of correlations amid the rate of chromosomal aberrations and the dose of gamma-rays were on the level 0.8–0.9. The fragments/bridges ratio is a clear and sufficient index for determining the nature of the mutagen agent. We distinguished the following types of chromosomal rearrangements: chromatid and chromosome bridges, single and double fragments, micronuclei, and delayed chromosomes. The ratio of chromosomal aberrations changes with the change in mutagen; note that bridge-types are characteristic of irradiation. Radiomutants are more resistant to gamma rays. This is apparent in the lower rate of chromosomal aberrations. Varieties obtained by chemical mutagenesis (varieties Sonechko, Kalinova) are more sensitive to gamma-irradiation than others. We propose these varieties as objects for a mutation breeding programme and radiation of mutants for planting in areas subject to the action of gamma-rays.

Carbon monoxide mitigates salt-induced inhibition of root growth and suppresses programmed cell death in wheat primary roots by inhibiting superoxide anion overproduction

In our experiments, treatment of wheat seedling roots with varying concentrations of NaCl caused the inhibition of primary root growth in a dose-dependent manner, which was consistent with the progressive DNA laddering in the primary root tips. Upon 100, and 200 mM NaCl stress, the increase of carbon monoxide (CO) release and heme oxygenase (HO) activity was observed. By contraries, treatment with 400 mM NaCl is otherwise, that the result displays a decreasing tendency. Besides DNA laddering, 200 mM NaCl treatment exhibited the induction of other programmed cell death (PCD) associated with phenomenon in the primary root tips, such as TUNEL staining, nuclear condense and deformation. Further, HO's catalytic product CO was able to dose-dependently mitigate 200 mM NaCl-induced inhibition of root growth and delay PCD. These effects were prevented strongly by incubation with DETC (a Cu/Zn-SOD inhibitor), and differentially influenced by Tiron (a scavenger of superoxide anion) and apocynin (an inhibitor of NADPH oxidase). Meanwhile, 50% CO aqueous solution inhibited the overproduction of superoxide anion, NADPH oxidase activities and corresponding transcript, and enhanced superoxide dismutase (SOD) activity, Mn-SOD and Cu/ Zn-SOD transcript. Taken together, the results suggested that CO might be involved in plant tolerance against salinity stress, and its alleviation of PCD and inhibition of root growth was related to the decrease of superoxide anion overproduction partially via up-regulation of SOD and down-regulation of NADPH oxidase expression.

Temperature and pH of the nutrient solution on wheat primary root growth

Primary root growth is very important for wheat (Triticum aestivum L.) crop in upland conditions in the State of São Paulo. Fourteen wheat genotypes (mutant lines and cultivars) were evaluated for primary root growth during 7 and 15 days of development in complete and aerated nutrient solutions, in the laboratory. In the first experiment, solutions with three pH values (4.0, 5.0 and 6.0) at constant temperature (24 ± 1°C), and in the second experiment, solutions with the same pH (4.0) but with three temperatures (18°C ± 1°C, 24°C ± 1°C and 30°C ± 1°C) were used. High genetic variability was observed among the evaluated genotypes in relation to primary root growth in the first stages of development in nutrient solutions independent of pH, temperature and growth period. Genotypes 6 (BH-1146) and 13 (IAC-17), tolerant to Al3+ showed genetic potential for root growth in the first stages of development (7 and 15 days), regardless of nutrient solution temperature and pH. Genotypes 14 (IAC-24 M), 15 (IAC-24), 17 (MON"S" / ALD "S") ´ IAC-24 M2, 18 (MON"S" / ALD "S") ´ IAC-24 M3 and 24 (KAUZ"S" / IAC-24 M3), tolerant to Al3+, showed reduced root growth under the same conditions.