College of Agriculture & Natural Resources

Permanent URI for this communityhttp://hdl.handle.net/1903/1598

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

Browse

Filters

2016 - 201942020 - 20223

Settings

Subject: search.filters.subject.Arabidopsis

Search Results

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Two Triacylglycerol Lipases Are Negative Regulators of Chilling Stress Tolerance in Arabidopsis
    (MDPI, 2022-03-21) Wang, Lang; Qian, Bilian; Zhao, Lei; Liang, Ming-Hua; Zhan, Xiangqiang; Zhu, Jianhua
    Cold stress is one of the abiotic stress conditions that severely limit plant growth and development and productivity. Triacylglycerol lipases are important metabolic enzymes for the catabolism of triacylglycerols and, therefore, play important roles in cellular activities including seed germination and early seedling establishment. However, whether they play a role in cold stress responses remains unknown. In this study, we characterized two Arabidopsis triacylglycerol lipases, MPL1 and LIP1 and defined their role in cold stress. The expression of MPL1 and LIP1 is reduced by cold stress, suggesting that they may be negative factors related to cold stress. Indeed, we found that loss-of-function of MPL1 and LIP1 resulted in increased cold tolerance and that the mpl1lip1 double mutant displayed an additive effect on cold tolerance. We performed RNA-seq analysis to reveal the global effect of the mpl1 and lip1 mutations on gene expression under cold stress. The mpl1 mutation had a small effect on gene expression under both under control and cold stress conditions whereas the lip1 mutation caused a much stronger effect on gene expression under control and cold stress conditions. The mpl1lip1 double mutant had a moderate effect on gene expression under control and cold stress conditions. Together, our results indicate that MPL1 and LIP1 triacylglycerol lipases are negative regulators of cold tolerance without any side effects on growth in Arabidopsis and that they might be ideal candidates for breeding cold-tolerant crops through genome editing technology.
  • Thumbnail Image
    Item
    Application of CRISPR-Cas12a temperature sensitivity for improved genome editing in rice, maize, and Arabidopsis
    (Springer Nature, 2019-01-31) Malzahn, Aimee A.; Tang, Xu; Lee, Keunsub; Ren, Qiurong; Sretenovic, Simon; Zhang, Yingxiao; Chen, Hongqiao; Kang, Minjeong; Bao, Yu; Zheng, Xuelian; Deng, Kejun; Zhang, Tao; Salcedo, Valeria; Wang, Kan; Zhang, Yong; Qi, Yiping
    CRISPR-Cas12a (formerly Cpf1) is an RNA-guided endonuclease with distinct features that have expanded genome editing capabilities. Cas12a-mediated genome editing is temperature sensitive in plants, but a lack of a comprehensive understanding on Cas12a temperature sensitivity in plant cells has hampered effective application of Cas12a nucleases in plant genome editing. We compared AsCas12a, FnCas12a, and LbCas12a for their editing efficiencies and non-homologous end joining (NHEJ) repair profiles at four different temperatures in rice. We found that AsCas12a is more sensitive to temperature and that it requires a temperature of over 28 °C for high activity. Each Cas12a nuclease exhibited distinct indel mutation profiles which were not affected by temperatures. For the first time, we successfully applied AsCas12a for generating rice mutants with high frequencies up to 93% among T0 lines. We next pursued editing in the dicot model plant Arabidopsis, for which Cas12a-based genome editing has not been previously demonstrated. While LbCas12a barely showed any editing activity at 22 °C, its editing activity was rescued by growing the transgenic plants at 29 °C. With an early high-temperature treatment regime, we successfully achieved germline editing at the two target genes, GL2 and TT4, in Arabidopsis transgenic lines. We then used high-temperature treatment to improve Cas12a-mediated genome editing in maize. By growing LbCas12a T0 maize lines at 28 °C, we obtained Cas12a-edited mutants at frequencies up to 100% in the T1 generation. Finally, we demonstrated DNA binding of Cas12a was not abolished at lower temperatures by using a dCas12a-SRDX-based transcriptional repression system in Arabidopsis. Our study demonstrates the use of high-temperature regimes to achieve high editing efficiencies with Cas12a systems in rice, Arabidopsis, and maize and sheds light on the mechanism of temperature sensitivity for Cas12a in plants.
  • Thumbnail Image
    Item
    Silicon modulates multi-layered defense against powdery mildew in Arabidopsis
    (Springer Nature, 2020-03-27) Wang, Lili; Dong, Min; Zhang, Qiong; Wu, Ying; Hu, Liang; Parson, James F.; Eisenstein, Edward; Du, Xiangge; Xiao, Shunyuan
    Silicon (Si) has been widely employed in agriculture to enhance resistance against pathogens in many crop plants. However, the underlying molecular mechanisms of Si-mediated resistance remain elusive. In this study, the Arabidopsis-powdery mildew pathosystem was employed to investigate possible defense mechanisms of Si-mediated resistance. Because Arabidopsis lacks efficient Si transporters and thus is a low Si-accumulator, two heterologous Si influx transporters (from barley and muskmelon) were individually expressed in wild-type Arabidopsis Col-0 and a panel of mutants defective in different immune signaling pathways. Results from infection tests showed that while very low leaf Si content slightly induced salicylic acid (SA)-dependent resistance, high Si promoted PAD4-dependent but largely EDS1- and SA-independent resistance against the adapted powdery mildew isolate Golovinomyces cichoracearum UCSC1. Intriguingly, our results also showed that high Si could largely reboot non-host resistance in an immune-compromised eds1/pad4/sid2 triple mutant background against a non-adapted powdery mildew isolate G. cichoracearum UMSG1. Taken together, our results suggest that assimilated Si modulates distinct, multi-layered defense mechanisms to enhance plant resistance against adapted and no-adapted powdery mildew pathogens, possibly via synergistic interaction with defense-induced callose.
  • Thumbnail Image
    Item
    Overexpression of AtAHL20 causes delayed flowering in Arabidopsis via repression of FT expression
    (Springer Nature, 2020-11-11) Tayengwa, Reuben; Sharma Koirala, Pushpa; Pierce, Courtney F.; Werner, Breanna E.; Neff, Michael M.
    The 29-member Arabidopsis AHL gene family is classified into three main classes based on nucleotide and protein sequence evolutionary differences. These differences include the presence or absence of introns, type and/or number of conserved AT-hook and PPC domains. AHL gene family members are divided into two phylogenetic clades, Clade-A and Clade-B. A majority of the 29 members remain functionally uncharacterized. Furthermore, the biological significance of the DNA and peptide sequence diversity, observed in the conserved motifs and domains found in the different AHL types, is a subject area that remains largely unexplored. Transgenic plants overexpressing AtAHL20 flowered later than the wild type under both short and long days. Transcript accumulation analyses showed that 35S:AtAHL20 plants contained reduced FT, TSF, AGL8 and SPL3 mRNA levels. Similarly, overexpression of AtAHL20’s orthologue in Camelina sativa, Arabidopsis’ closely related Brassicaceae family member species, conferred a late-flowering phenotype via suppression of CsFT expression. However, overexpression of an aberrant AtAHL20 gene harboring a missense mutation in the AT-hook domain’s highly conserved R-G-R core motif abolished the late-flowering phenotype. Data from targeted yeast-two-hybrid assays showed that AtAHL20 interacted with itself and several other Clade-A Type-I AHLs which have been previously implicated in flowering-time regulation: AtAHL19, AtAHL22 and AtAHL29. We showed via gain-of-function analysis that AtAHL20 is a negative regulator of FT expression, as well as other downstream flowering time regulating genes. A similar outcome in Camelina sativa transgenic plants overexpressing CsAHL20 suggest that this is a conserved function. Our results demonstrate that AtAHL20 acts as a photoperiod-independent negative regulator of transition to flowering.
  • Thumbnail Image
    Item
    The MEIOTIC PROPHASE AMINOPEPTIDASE 1 regulates polyploidy in Arabidopsis thaliana
    (2017) Wattarantenne, Kasuni Vishwaprabha; Peer, Wendy A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Growth and development in plants is dependent on cellular functions such as cell cycle progression. M1 aminopeptidases have been shown to regulate mitosis and meiosis in animals. MEIOTIC PROPHASE AMINOPEPTIDASE M1 (MPA1) in Arabidopsis thaliana was previously shown to regulate cell cycle progression during prophase I in meiosis I in both female and male gametophytes and be essential for homologous recombination. mpa1 homozygous embryos are lethal due to chromosome de-synapsis resulting in uneven distribution of chromosomes in daughter cells and massive decrease in homologous crossovers reduces independent assortment. Here, I show that MPA1 is a soluble protein and is expressed throughout the seedling: in the primary root, hypocotyl, cotyledons, petioles and root and shoot apical meristem. I isolated and characterized four mpa1 alleles, and I showed that MPA1 loss-of-function mutants exhibited three significant phenotypes corresponding to development in seedlings and adult plants in Arabidopsis: non-disjunction in mitotic cells, altered polyploidy, and temporary arrest of primary root growth during seedling establishment.
  • Thumbnail Image
    Item
    INVESTIGATION OF ARABIDOPSIS TSO1, A REGULATOR OF CELL PROLIFERATION AND DIFFERENTIATION
    (2017) WANG, WANPENG; Liu, Zhongchi; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Multicellular eukaryotic organisms build complex body structures from a single cell. Through coordinated cell proliferation and differentiation, the collective behavior of cells forms organs that achieve physiological functions. Underlying the developmental processes are the molecular machineries that integrate cell cycle regulation with cell fate acquisition. While animal organogenesis occurs early during embryogenesis, plants maintain pluripotent stem cells at the growing tips (meristems) and generate organs iteratively throughout lifespan. The amazing ability to balance stem cell self-renewal and differentiation underlies the extreme longevity of some plants species. Despite the differences, common mechanisms exist across plant and animal developmental regulation. Understanding both unique and common mechanisms of plant development has broad implications on basic science as well as agriculture and medicine. The Arabidopsis TSO1 gene is a regulator of cell proliferation and differentiation at the shoot and root meristems. TSO1 encodes a CXC domain protein and its animal homologs encode core components of a cell cycle regulatory complex, the DREAM complex. To investigate TSO1 function and identify factors that act together with TSO1, I carried out two genetic screens for suppressors and enhancers of tso1 mutants. I discovered that loss-of-function mutations in MYB3R1, which encodes the Arabidopsis ortholog of human B-Myb, can suppress tso1 mutant defects at both the shoot and root meristems. In tso1-1 mutant, MYB3R1 is over and ectopically expressed at the shoot and root meristems. Furthermore, MYB3R1 phospho mimic enhanced the tso1-3 phenotype, indicating that hyper-active MYB3R1 may mediate the tso1-1 phenotype. TSO1 physically interacts with MYB3R1 and likely forms a plant DREAM-like complex that operates in the plant meristems to balance cell proliferation with differentiation. A gain-of-function mutation of a HD-ZIP III transcription factor, REVOLUTA (REV), was identified as an enhancer of tso1 mutants. TSO1 directly represses REV transcription to balance adaxial and abaxial polarity of lateral organs and maintains the shoot apical meristem. This genetic and molecular interaction between TSO1 and the adaxial factor REV presents an integration point of cell cycle, lateral organ polarity, and meristem regulation. Together, our findings demonstrate a cell cycle regulatory module conserved across plants and animals and describe its integration into plant specific developmental context.
  • Thumbnail Image
    Item
    IDENTIFICATION AND CHARACTERIZATION OF IAA OXIDASES AND THEIR ROLE IN IAA HOMEOSTATIC REGULATION IN ARABIDOPSIS
    (2016) Zhang, Jun; Peer, Wendy Ann; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Auxin is a crucial plant hormone that shapes and directs plant growth. Indole-3-acetic acid (IAA) is the predominant auxin in nature. Auxin regulates cell expansion and cell division in a dose dependent way. Therefore, plants evolved an extremely complex yet highly coordinated network to maintain auxin homeostasis, including IAA biosynthesis, transport, conjugation and oxidation. Among these, the least known process is IAA oxidation. Discovering how IAA is terminated is very important in completing the whole picture of IAA homeostatic regulation. By partial purification of IAA oxidases from Arabidopsis, we detected IAA oxidation activity from both microsomal fractions and soluble fractions. We first investigated the protein in microsomal fraction and identified one oxidase named as ACC oxidase 2 (ACO2), an ethylene synthetase that belongs to 2-oxoglutarate and iron (II) [2OG(Fe)] dependent dioxygenase family. In vitro enzyme assays with IAA showed that ACO2 could catabolize IAA and that the product had the same retention time as indole-3-carbinal (ICA), an decarboxylative IAA oxidation product. The same enzyme assay with the ACO2 homologues ACO3 was conducted, and ACO3 showed similar activity. An ACO2 loss-of-function allele showed ethylene related phenotypes, including longer hypocotyls and reduced apical hook angle in etiolated seedlings, and delayed bolting. Further, null aco2 mutants also showed reduced phototropic bending, a typical auxin related phenotype. These results indicate that ACO2 might be involved in both ethylene and auxin signaling. We also investigated the soluble IAA oxidases, AtDAO1 (DAO1) and AtDAO2 (DAO2). In vitro enzyme assays showed that both recombinant DAO1 and DAO2 have IAA oxidation activity and the product is the non-decarboxylated 2-oxindole-3-acetic acid (oxIAA), the major IAA metabolite observed under normal growth conditions. Analysis of the loss-of-function null allele dao1-1 showed that DAO1 is the predominant IAA oxidase and is responsible for 95% of oxIAA production in Arabidopsis seedlings. Dysregulation of IAA oxidation altered the IAA metabolism profile and causes accumulation of other IAA conjugates and a series of morphological alteration, including elongation of organs, increased lateral roots and delayed sepal opening. Investigation of expression patterns shows that DAO1 is a cytosolic protein that widely expressed throughout the plant, especially in the root tip, the pericycle of root, the cotyledon, and the sepal, highly correlating to the phenotypes of dao1-1. These results suggest that IAA oxidation plays an important role in IAA homeostasis during the whole life of Arabidopsis.