The Plant Journal

doi: 10.1111/tpj.13694pmid: N/A

McCormick, Sheila

doi: 10.1111/tpj.14054pmid: N/A

Fukuda, Makiha; Wakuta, Shinji; Kamiyo, Jio; Fujiwara, Toru; Takano, Junpei

doi: 10.1111/tpj.13985pmid: 29882321

Boron (B) is an essential micronutrient for plants. To maintain B concentration in tissues at appropriate levels, plants use boric acid channels belonging to the NIP subfamily of aquaporins and BOR borate exporters. To regulate B transport, these transporters exhibit different cell‐type specific expression, polar localization, and B‐dependent post‐transcriptional regulation. Here, we describe the development of genetically encoded biosensors for cytosolic boric acid to visualize the spatial distribution and temporal dynamics of B in plant tissues. The biosensors were designed based on the function of the NIP5;1 5′‐untranslated region (UTR), which promotes mRNA degradation in response to an elevated cytosolic boric acid concentration. The signal intensities of the biosensor coupled with Venus fluorescent protein and a nuclear localization signal (uNIP5;1‐Venus) showed negative correlation with intracellular B concentrations in cultured tobacco BY‐2 cells. When expressed in Arabidopsis thaliana, uNIP5;1‐Venus enabled the quantification of B distribution in roots at single‐cell resolution. In mature roots, cytosolic B levels in stele were maintained under low B supply, while those in epidermal, cortical, and endodermal cells were influenced by external B concentrations. Another biosensor coupled with a luciferase protein fused to a destabilization PEST sequence (uNIP5;1‐Luc) was used to visualize changes in cytosolic boric acid concentrations. Thus, uNIP5;1‐Venus/Luc enables visualization of B transport in various plant cells/tissues.

Wei, Kun; Wang, Jing; Sang, Mengmeng; Zhang, Shilong; Zhou, Houchao; Jiang, Libo; Clavijo Michelangeli, Jose A.; Vallejos, C. Eduardo; Wu, Rongling

doi: 10.1111/tpj.13986pmid: 29882297

Crop modeling, a widely used tool to predict plant growth and development in heterogeneous environments, has been increasingly integrated with genetic information to improve its predictability. This integration can also shed light on the mechanistic path that connects the genotype to a particular phenotype under specific environments. We implemented a bivariate statistical procedure to map and identify quantitative trait loci (QTLs) that can predict the form of plant growth by estimating cultivar‐specific growth parameters and incorporating these parameters into a mapping framework. The procedure enables the characterization of how QTLs act differently in response to developmental and environmental cues. We used this procedure to map growth parameters of leaf area and mass in a mapping population of the common bean (Phaseolus vulgaris L.). Different sets of QTLs are responsible for various aspects of growth, including the initiation time of growth, growth rate, inflection point and asymptotic growth. A major QTL of a large effect was identified to pleiotropically affect trait expression in distinct environments and different traits expressed on the same organism. The integration of crop models and QTL mapping through our statistical procedure provides a powerful means of building a more precise predictive model of genotype‐phenotype relationships for crops.

Gao, Long; Guo, Xue; Liu, Xue‐Qiong; Zhang, Li; Huang, Jilei; Tan, Li; Lin, Zhen; Nagawa, Shingo; Wang, Dan‐Yang

doi: 10.1111/tpj.13987pmid: 29882345

Changes in the amount of mitochondrial DNA (mtDNA) have never been investigated in plant zygotes or early plant embryos due to the difficulty in isolating these cells, although such changes have been investigated in mammalian embryos. Using the single‐cell quantitative real‐time polymerase chain reaction (PCR) and laser confocal microscopy, we surveyed the changes in mtDNA levels during early embryogenesis in Torenia fournieri and Arabidopsis thaliana. In contrast with the amount of mtDNA in early mammalian embryos, which does not change, we found that mtDNA doubling occurred during zygotic development in T. fournieri and during two‐cell proembryo development in A. thaliana. These findings reveal that mtDNA doubling occurs during early embryogenesis in T. fournieri and A. thaliana, indicating that the dynamics of mtDNA in early plant embryos differs from that in early mammalian embryos.

Takeda, Yuri; Tobimatsu, Yuki; Karlen, Steven D.; Koshiba, Taichi; Suzuki, Shiro; Yamamura, Masaomi; Murakami, Shinya; Mukai, Mai; Hattori, Takefumi; Osakabe, Keishi; Ralph, John; Sakamoto, Masahiro; Umezawa, Toshiaki

Gritsunov, Artyom; Peek, James; Diaz Caballero, Julio; Guttman, David; Christendat, Dinesh

doi: 10.1111/tpj.13989pmid: 29890023

Quinate is produced and used by many plants in the biosynthesis of chlorogenic acids (CGAs). Chlorogenic acids are astringent and serve to deter herbivory. They also function as antifungal agents and have potent antioxidant properties. Quinate is produced at a branch point of shikimate biosynthesis by the enzyme quinate dehydrogenase (QDH). However, little information exists on the identity and biochemical properties of plant QDHs. In this study, we utilized structural and bioinformatics approaches to establish a QDH‐specific primary sequence motif. Using this motif, we identified QDHs from diverse plants and confirmed their activity by recombinant protein production and kinetic assays. Through a detailed phylogenetic analysis, we show that plant QDHs arose directly from bifunctional dehydroquinate dehydratase–shikimate dehydrogenases (DHQD‐SDHs) through different convergent evolutionary events, illustrated by our findings that eudicot and conifer QDHs arose early in vascular plant evolution whereas Brassicaceae QDHs emerged later. This process of recurrent evolution of QDH is further demonstrated by the fact that this family of proteins independently evolved NAD+ and NADP+ specificity in eudicots. The acquisition of QDH activity by these proteins was accompanied by the inactivation or functional evolution of the DHQD domain, as verified by enzyme activity assays and as reflected in the loss of key DHQD active site residues. The implications of QDH activity and evolution are discussed in terms of plant growth and development.

Carrington, Yuriko; Guo, Jia; Le, Cuong H.; Fillo, Alexander; Kwon, Junsu; Tran, Lan T.; Ehlting, Jürgen

doi: 10.1111/tpj.13990pmid: 29894016

The shikimate pathway synthesizes aromatic amino acids essential for protein biosynthesis. Shikimate dehydrogenase (SDH) is a central enzyme of this primary metabolic pathway, producing shikimate. The structurally similar quinate is a secondary metabolite synthesized by quinate dehydrogenase (QDH). SDH and QDH belong to the same gene family, which diverged into two phylogenetic clades after a defining gene duplication just prior to the angiosperm/gymnosperm split. Non‐seed plants that diverged before this duplication harbour only a single gene of this family. Extant representatives from the chlorophytes (Chlamydomonas reinhardtii), bryophytes (Physcomitrella patens) and lycophytes (Selaginella moellendorfii) encoded almost exclusively SDH activity in vitro. A reconstructed ancestral sequence representing the node just prior to the gene duplication also encoded SDH activity. Quinate dehydrogenase activity was gained only in seed plants following gene duplication. Quinate dehydrogenases of gymnosperms, represented here by Pinus taeda, may be reminiscent of an evolutionary intermediate since they encode equal SDH and QDH activities. The second copy in P. taeda maintained specificity for shikimate similar to the activity found in the angiosperm SDH sister clade. The codon for a tyrosine residue within the active site displayed a signature of positive selection at the node defining the QDH clade, where it changed to a glycine. Replacing the tyrosine with a glycine in a highly shikimate‐specific angiosperm SDH was sufficient to gain some QDH function. Thus, very few mutations were necessary to facilitate the evolution of QDH genes.

Yang, Luming; Liu, Hanqiang; Zhao, Jianyu; Pan, Yupeng; Cheng, Siyuan; Lietzow, Calvin D.; Wen, Changlong; Zhang, Xiaolan; Weng, Yiqun

doi: 10.1111/tpj.13991pmid: 29901823

Plants employ tight genetic control to integrate intrinsic growth signals and environmental cues to enable organs to grow to a defined size. Many genes contributing to cell proliferation and/or cell expansion, and consequently organ size control, have been identified, but the regulatory pathways are poorly understood. Here we have characterized a cucumber littleleaf (ll) mutant which exhibits smaller organ sizes but more lateral branches than the wild type. The small organ size in ll was due to a reduction of both cell number and cell size. Quantitative trait locus (QTL) analyses revealed co‐localization of major‐effect QTLs for fruit size, fruit and seed weight, as well as number of lateral branches, with the LL locus indicating pleiotropic effects of the ll mutation. We demonstrate that LL is an ortholog of Arabidopsis STERILE APETALA (SAP) encoding a WD40 repeat domain‐containing protein; the mutant protein differed from the wild type by a single amino acid substitution (W264G) in the second WD40 repeat. W264 was conserved in 34 vascular plant genomes examined. Phylogenetic analysis suggested that LL originated before the emergence of flowering plants but was lost in the grass genome lineage. The function of LL in organ size control was confirmed by its overexpression in transgenic cucumbers and ectopic expression in Arabidopsis. Transcriptome profiling in LL and ll bulks revealed a complex regulatory network for LL‐mediated organ size variation that involves several known organ size regulators and associated pathways. The data support LL as an important player in organ size control and lateral branch development in cucumber.

Ferretti, Ursula; Ciura, Joanna; Ksas, Brigitte; Rác, Marek; Sedlářová, Michaela; Kruk, Jerzy; Havaux, Michel; Pospíšil, Pavel

doi: 10.1111/tpj.13993pmid: 29901834

Prenylquinols (tocochromanols and plastoquinols) serve as efficient physical and chemical quenchers of singlet oxygen (1O2) formed during high light stress in higher plants. Although quenching of 1O2 by prenylquinols has been previously studied, direct evidence for chemical quenching of 1O2 by plastoquinols and their oxidation products is limited in vivo. In the present study, the role of plastoquinol‐9 (PQH2‐9) in chemical quenching of 1O2 was studied in Arabidopsis thaliana lines overexpressing the SOLANESYL DIPHOSPHATE SYNTHASE 1 gene (SPS1oex) involved in PQH2‐9 and plastochromanol‐8 biosynthesis. In this work, direct evidence for chemical quenching of 1O2 by plastoquinols and their oxidation products is presented, which is obtained by microscopic techniques in vivo. Chemical quenching of 1O2 was associated with consumption of PQH2‐9 and formation of its various oxidized forms. Oxidation of PQH2‐9 by 1O2 leads to plastoquinone‐9 (PQ‐9), which is subsequently oxidized to hydroxyplastoquinone‐9 [PQ(OH)‐9]. We provide here evidence that oxidation of PQ(OH)‐9 by 1O2 results in the formation of trihydroxyplastoquinone‐9 [PQ(OH)3‐9]. It is concluded here that PQH2‐9 serves as an efficient 1O2 chemical quencher in Arabidopsis, and PQ(OH)3‐9 can be considered as a natural product of 1O2 reaction with PQ(OH)‐9. The understanding of the mechanisms underlying 1O2 chemical quenching provides information on the role of plastoquinols and their oxidation products in the response of plants to photooxidative stress.