Temperature change is of potential to trigger the formation of unreduced gametes. In this study, we showed that short periods of high temperature treatment can induce the production of 2n pollen in ...Populus pseudo-simonii Kitag. The meiotic stage, duration of treatment, and temperature have significant effects on the induction of 2n pollen. Heat stress resulted in meiotic abnormalities, including failure of chromosome separation, chromosome stickiness, laggards and micronuclei. Spindle disorientations in the second meiotic division, such as parallel, fused, and tripolar spindles, either increased in frequency or were induced de novo by high temperature treatment. We found that the high temperature treatment induced depolymerisation of meiotic microtubular cytoskeleton, resulting in the failure of chromosome segregation. New microtubular cytoskeletons were able to repolymerise in some heat-treated cells after transferring them to normal conditions. However, aberrant cytokinesis occurred owing to defects of new radial microtubule systems, leading to production of monads, dyads, triads, and polyads. This suggested that depolymerisation and incomplete restoration of microtubules may be important for high temperature-induction of unreduced gametes. These findings might help us understand how polyploidisation is induced by temperature-related stress and support the potential effects of global climate change on reproductive development of plants.
Abstract
Leaves provide energy for plants, and consequently for animals, through photosynthesis. Despite their important functions, plant leaf developmental processes and their underlying mechanisms ...have not been well characterized. Here, we provide a holistic description of leaf developmental processes that is centered on cytokinins and their signaling functions. Cytokinins maintain the growth potential (pluripotency) of shoot apical meristems, which provide stem cells for the generation of leaf primordia during the initial stage of leaf formation; cytokinins and auxins, as well as their interaction, determine the phyllotaxis pattern. The activities of cytokinins in various regions of the leaf, especially at the margins, collectively determine the final leaf morphology (e.g., simple or compound). The area of a leaf is generally determined by the number and size of the cells in the leaf. Cytokinins promote cell division and increase cell expansion during the proliferation and expansion stages of leaf cell development, respectively. During leaf senescence, cytokinins reduce sugar accumulation, increase chlorophyll synthesis, and prolong the leaf photosynthetic period. We also briefly describe the roles of other hormones, including auxin and ethylene, during the whole leaf developmental process. In this study, we review the regulatory roles of cytokinins in various leaf developmental stages, with a focus on cytokinin metabolism and signal transduction processes, in order to shed light on the molecular mechanisms underlying leaf development.
After polyploidization, plants usually undergo some morphological and physiological changes, including the lignin content of polyploids usually becoming lower than that of diploids. However, the ...regulatory mechanism of the variation of lignin content in polyploid plants remains unclear. Therefore, in this research, we used full-sib poplar triploids and diploids to explore the molecular regulatory basis of lignin content in poplar triploid leaves through the determination of lignin content, the observation of xylem cells, and transcriptome sequencing. The results showed that the lignin content of triploid leaves was significantly lower than that of diploid leaves. The xylem cells of triploid leaves were significantly larger than those of diploids. Transcriptome sequencing data show that most lignin biosynthesis genes were significantly downregulated, and genes related to cell growth were mostly upregulated in triploid leaves compared with diploid leaves. In addition, co-expression network analysis showed that several transcription factors might be involved in the regulation of lignin biosynthesis. Consequently, the altered expression of genes related to lignin might lead to the reduced lignin content in triploids. These results provide a theoretical basis for further exploring the molecular mechanism of the variation of polyploid lignin content and the utilization of polyploid lignocellulosic resources.
Allotriploid poplar has a prominent vegetative growth advantage that impacts dramatically on lumber yield. The growth regulation is complex which involves abundant genes, metabolic and signaling ...pathways, while the information about the functional control process is very little. We used high-throughput sequencing and physiological index measurement to obtain a global overview of differences between allotriploid and diploid
. The genes related to plant growth advantage show a higher expression compared to diploid, and most of them are revolved around hormones, photosynthesis and product accumulation. Thus, allotriploid
showed more efficient photosynthesis, carbon fixation, sucrose and starch synthesis, and metabolism as well as augmented biosynthesis of auxin, cytokinin, and gibberellin. These data enable the connection of metabolic processes, signaling pathways, and specific gene activity, which will underpin the development of network models to elucidate the process of triploid
advantage growth.
Breeding for dwarfism is an important approach to improve lodging resistance. Here, we performed comparative analysis of the phenotype, transcriptome, and hormone contents between diploids and ...tetraploids of poplar 84K (Populus alba × P. glandulosa). Compared with diploids, the indole-3-acetic acid (IAA) and gibberellin (GA3) contents were increased, whereas the jasmonic acid (JA) and abscisic acid (ABA) contents were decreased in tetraploids. RNA-sequencing revealed that differentially expressed genes (DEGs) in leaves of tetraploids were mainly involved in plant hormone pathways. Most DEGs associated with IAA and GA promotion of plant growth and development were downregulated, whereas most DEGs associated with ABA and JA promotion of plant senescence were upregulated. Weighted gene co-expression network analysis indicated that certain transcription factors may be involved in the regulation of genes involved in plant hormone pathways. Thus, the altered expression of some genes in the plant hormone pathways may lead to a reduction in IAA and GA contents, as well as an elevation in ABA and JA contents, resulting in the dwarfing of tetraploids. The results show that polyploidization is a complex biological process affected by multiple plant hormone signals, and it provides a foundation for further exploration of the mechanism of tetraploids dwarfing in forest trees.
Populus
is an important economical woody species due to its fast growth. In vitro induction of hexaploidy and investigation of morphological and anatomical characteristics in ((
Populus alba
×
P. ...glandulosa
) ×
P. tomentosa
) were conducted in this study. Chromosome doubling was induced in vitro in a triploid clone ((
Populus alba
×
P. glandulosa
) ×
P. tomentosa
) with oryzalin as a tubulin inhibitor. Nodal sections of 5 and 10 mm were exposed to 2.5 and 5.0 mg l
−1
oryzalin for 24, 48 and 72 h. No significant differences in survival rates were observed between the different oryzalin dose, exposure time or nodal length; however, all rates were significantly lower than those in the no-oryzalin controls. The highest frequency of hexaploidy was 100% for the treatment of 5-mm nodes with 5 mg l
−1
oryzalin for 72 h and the treatment of 10-mm nodes with 5 mg l
−1
oryzalin for 24 h. The hexaploid plants were distinguishable from the triploid plants by morphological and anatomical characteristics. Chromosome doubling was accompanied by increases in the thickness and chlorophyll content of leaves. The stomata of hexaploids were larger and had a lower density than those of the original triploids. In particular, in triploid-to-hexaploid conversion, roots were less abundant, were shorter and had larger diameters. Root characteristics were determined to be suitable parameters for identifying putative hexaploids because they can be easily and quickly assessed.
Key message
In vitro induction of hexaploidy and investigation of morphological and anatomical characteristics of ((
Populus alba
×
P. glandulosa
) ×
P. tomentosa
) at different ploidy levels were conducted in this study.
GATA transcription factors have been demonstrated to play key regulatory roles in plant growth, development, and hormonal response. However, the knowledge concerning the evolution of GATA genes in ...Eucalyptus urophylla and their trans-regulatory interaction is indistinct. Phylogenetic analysis and study of conserved motifs, exon structures, and expression patterns resolved the evolutionary relationships of these GATA proteins. Phylogenetic analysis showed that EgrGATAs are broadly distributed in four subfamilies. Cis-element analysis of promoters revealed that EgrGATA genes respond to light and are influenced by multiple hormones and abiotic stresses. Transcriptome analysis revealed distinct temporal and spatial expression patterns of EgrGATA genes in various tissues of E. urophylla S.T.Blake, which was confirmed by real-time quantitative PCR (RT-qPCR). Further research revealed that EurGNC and EurCGA1 were localized in the nucleus, and EurGNC directly binds to the cis-element of the EurGUN5 promoter, implying its potential roles in the regulation of chlorophyll synthesis. This comprehensive study provides new insights into the evolution of GATAs and could help to improve the photosynthetic assimilation and vegetative growth of E. urophylla at the genetic level.
Lycium ruthenicum of Solanaceae was widely used as healthy vegetables and natural medicine foods for containing numerous functional components in leaves, roots and fruits. In the present study, ...tetraploid plants of L. ruthenicum were obtained efficiently by treating their leaves with colchicine in vitro. The highest induction frequency of the tetraploids was 31.4%, which was obtained by preculturing the leaves for 10 days and then treating them with 100 mg/L of colchicine concentration for 48 h. The ploidy levels of the regenerated plants were determined by flow cytometry and chromosome counting methods. Cytological, morphological, and histological characterization validated the results of flow cytometry, revealing the differences between the two kinds of ploidy plants in their tissue culture stage and field production stages. Morphological indexes also provide a simple and intuitionistic method for distinguishing tetraploid from diploid plants. As the chromosome number increased, the stomatal size and number of the chloroplasts in the stomata also increased, but the stomatal density decreased. The results indicate that the chromosome number is correlated with the stomatal index. The generated tetraploid is a potentially useful cultivated variety and will be beneficial for producing triploid progeny in the future.
Drought-induced forest death has become a global phenomenon, which is hindering the development of sustainable forestry. Polyploidy breeding has been considered as an effective method of genetic ...improvement for tree stress resistance. However, the response mechanisms of tetraploid poplars to drought stress are unclear. In this study, based on high-throughput sequencing of transcriptome, small RNA, and degradome for these samples, which selected three genotypes of tetraploid poplars and their counterpart diploids for drought stress and rewatering trial in the experiment, we performed multi-omics analyses to investigate the distinction in drought resistance between tetraploid and diploid. A total of 3391 differentially expressed genes (DEGs) were found from the Dro-Di vs. CK-Di, 3753 DEGs from the Re-Di vs. Dro-Di, 3857 DEGs from the Dro-Te vs. CK-Te, and 4177 DEGs from the Re-Te vs. Dro-Te. Of the above DEGs, 1646 common-DEGs were identified significantly related to drought-stress response, 2034 common-DEGs related to rewater response, 158 and 114 common-DEGs showed opposite expression patterns between diploid and tetraploid, implying that these DEGs might play important roles in response to drought stress as a result of differences in ploidy. Additionally, 586 known miRNAs and 72 novel miRNAs were identified through analysis of 18 small RNA libraries, among which eight common-miRNAs were significantly related to drought-stress response, and four were related to rewater response. The degradome sequencing analysis revealed that 154 target transcripts for 24 drought-stress-associated differentially expressed miRNAs (DEmiRs), and 90 for 12 rewatering-associated DEmiRs were identified in the tetraploid based on both degradome and TargetFinder analyses. These findings provide valuable information for further functional characterization of genes and miRNAs in response to drought stress in Populus polyploidy, and potentially contribute to drought-resistant breeding of polypoid in the future.
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