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Early View

  Special Issue: Genomics-assisted Germplasm Improvement in Rice
Ectopic expression of fungal EcGDH improves nitrogen assimilation and grain yield in rice
Author: Dongying Tang, Yuchong Peng, Jianzhong Lin, Changqing Du, Yuanzhu Yang, Dan Wang, Cong Liu, Lu Yan, Xiaoying Zhao, Xia Li, Liangbi Chen and Xuanming Liu
Received: December 28, 2016         Accepted: January 5, 2017
Online Date: January 6, 2017
DOI: 10.1111/jipb.12519
   
      
    

NADP(H)-dependent glutamate dehydrogenases (GDH) in lower organisms have stronger ammonium affinity than those in higher plants. Here we report that transgenic rice overexpressing the EcGDH from Eurotium cheralieri exhibited significantly enhanced aminating activities. Hydroponic and field tests showed that nitrogen assimilation efficiency and grain yields were markedly increased in these transgenic plants, especially at the low nitrogen conditions. These results suggest that EcGDH may have potential to be used to improve nitrogen assimilation and grain yield in rice.

Abstract (Browse 168)   |   References   |   Full Text HTML   |   Full Text PDF       
QTL editing confers opposing yield performance in different rice varieties
Author: Lan Shen, Chun Wang, Yaping Fu, Junjie Wang, Qing Liu, Xiaoming Zhang, Changjie Yan, Qian Qian and Kejian Wang
Received: June 1, 2016         Accepted: September 13, 2016
Online Date: September 15, 2016
DOI: 10.1111/jipb.12501
   
      
    

Grain yield is one of the most important and complex trait for genetic improvement in crops; it is known to be controlled by a number of genes known as quantitative trait loci (QTLs). In the past decade, many yield-contributing QTLs have been identified in crops. However, it remains unclear whether those QTLs confer the same yield performance in different genetic backgrounds. Here, we performed CRISPR/Cas9-mediated QTL editing in five widely-cultivated rice varieties and revealed that the same QTL can have diverse, even opposing, effects on grain yield in different genetic backgrounds.

Abstract (Browse 245)   |   References   |   Full Text HTML   |   Full Text PDF       
  Special Issue: Plant Vascular Biology
Transcript profiling of a novel plant meristem, the monocot cambium
Author: Matthew Zinkgraf, Suzanne Gerttula and Andrew Groover
Received: February 18, 2017         Accepted: March 15, 2017
Online Date: March 17, 2017
DOI: 10.1111/jipb.12538
   
      
    

While monocots lack the ability to produce a vascular cambium or woody growth, some monocot lineages evolved a novel lateral meristem, the monocot cambium, which supports secondary radial growth of stems. In contrast to the vascular cambium found in woody angiosperm and gymnosperm species, the monocot cambium produces secondary vascular bundles, which have an amphivasal organization of tracheids encircling a central strand of phloem. Currently there is no information concerning the molecular genetic basis of the development or evolution of the monocot cambium. Here we report high-quality transcriptomes for monocot cambium and early derivative tissues in two monocot genera, Yucca and Cordyline. Monocot cambium transcript profiles were compared to those of vascular cambia and secondary xylem tissues of two forest tree species, Populus trichocarpa and Eucalyptus grandis. Monocot cambium transcript levels showed that there are extensive overlaps between the regulation of monocot cambia and vascular cambia. Candidate regulatory genes that vary between the monocot and vascular cambia were also identified, and included members of the KANADI and CLE families involved in polarity and cell-cell signaling, respectively. We suggest that the monocot cambium may have evolved in part through reactivation of genetic mechanisms involved in vascular cambium regulation.

Abstract (Browse 111)   |   References   |   Full Text HTML   |   Full Text PDF       
The fungal UmSrt1 and maize ZmSUT1 sucrose transporters battle for plant sugar resources
Author: Anke Wittek, Ingo Dreyer, Khaled A.S. Al-Rasheid, Norbert Sauer, Rainer Hedrich and Dietmar Geiger
Received: March 1, 2017         Accepted: March 10, 2017
Online Date: March 15, 2017
DOI: 10.1111/jipb.12535
   
      
    

The biotrophic fungus Ustilago maydis causes corn smut disease, inducing tumor formation in its host Zea mays. Upon infection, the fungal hyphae invaginate the plasma membrane of infected maize cells, establishing an interface where pathogen and host are separated only by their plasma membranes. At this interface the fungal and maize sucrose transporters, UmSrt1 and ZmSUT1, compete for extracellular sucrose in the corn smut/maize pathosystem. Here we biophysically characterized ZmSUT1 and UmSrt1 in Xenopus oocytes with respect to their voltage-, pH- and substrate-dependence and determined affinities toward protons and sucrose. In contrast to ZmSUT1, UmSrt1 has a high affinity for sucrose and is relatively pH- and voltage-independent. Using these quantitative parameters, we developed a mathematical model to simulate the competition for extracellular sucrose at the contact zone between the fungus and the host plant. This approach revealed that UmSrt1 exploits the apoplastic sucrose resource, which forces the plant transporter into a sucrose export mode providing the fungus with sugar from the phloem. Importantly, the high sucrose concentration in the phloem appeared disadvantageous for the ZmSUT1, preventing sucrose recovery from the apoplastic space in the fungus/plant interface.

Abstract (Browse 103)   |   References   |   Full Text HTML   |   Full Text PDF       
Implications of nitrogen phloem loading for carbon metabolism and transport during Arabidopsis development
Author: James P. Santiago and Mechthild Tegeder
Received: February 25, 2017         Accepted: March 9, 2017
Online Date: March 14, 2017
DOI: 10.1111/jipb.12533
   
      
    

Metabolite transport processes and primary metabolism are highly interconnected. This study examined the importance of source-to-sink nitrogen partitioning, and associated nitrogen metabolism for carbon capture, transport and usage. Specifically, Arabidopsis aap8 (AMINO ACID PERMEASE 8) mutant lines were analyzed to resolve the consequences of reduced amino acid phloem loading for source leaf carbon metabolism, sucrose phloem transport and sink development during vegetative and reproductive growth phase. Results showed that decreased amino acid transport had a negative effect on sink development of aap8 lines throughout the life cycle, leading to an overall decrease in plant biomass. During vegetative stage, photosynthesis and carbohydrate levels were decreased in aap8 leaves, while expression of carbon metabolism and transport genes, as well as sucrose phloem transport were not affected despite reduced sink strength. However, when aap8 plants transitioned to reproductive phase, carbon fixation and assimilation as well as sucrose partitioning to siliques were strongly decreased. Overall, this work demonstrates that phloem loading of nitrogen has varying implications for carbon fixation, assimilation and source-to-sink allocation depending on plant growth stage. It further suggests alterations in source-sink relationships, and regulation of carbon metabolism and transport by sink strength in a development-dependent manner.

Abstract (Browse 107)   |   References   |   Full Text HTML   |   Full Text PDF       
Sucrose transporter2 contributes to maize growth, development, and crop yield
Author: Kristen A Leach, Thu M Tran, Thomas L Slewinski, Robert B Meeley and David M Braun
Received: December 30, 2016         Accepted: February 10, 2017
Online Date: February 16, 2017
DOI: 10.1111/jipb.12527
   
      
    

During daylight, plants produce excess photosynthates, including sucrose, which is temporarily stored in the vacuole. At night, plants remobilize sucrose to sustain metabolism and growth. Based on homology to other sucrose transporter (SUT) proteins, we hypothesized the maize (Zea mays) SUCROSE TRANSPORTER2 (ZmSUT2) protein functions as a sucrose/H+ symporter on the vacuolar membrane to export transiently stored sucrose. To understand the biological role of ZmSut2, we examined its spatial and temporal gene expression, determined the protein subcellular localization, and characterized loss-of-function mutations. ZmSut2 mRNA was ubiquitously expressed and exhibited diurnal cycling in transcript abundance. Expressing a translational fusion of ZmSUT2 fused to a red fluorescent protein in maize mesophyll cell protoplasts revealed that the protein localized to the tonoplast. Under field conditions, zmsut2 mutant plants grew slower, possessed smaller tassels and ears, and produced fewer kernels when compared to wild-type siblings. zmsut2 mutants also accumulated two-fold more sucrose, glucose, and fructose as well as starch in source leaves compared to wild type. These findings suggest (i) ZmSUT2 functions to remobilize sucrose out of the vacuole for subsequent use in growing tissues; and (ii) its function provides an important contribution to maize development and agronomic yield.

Abstract (Browse 115)   |   References   |   Full Text HTML   |   Full Text PDF       
  Cell and Developmental Biology
Poly(ADP-ribose) polymerases regulate cell division and development in Arabidopsis roots
Author: Caifeng Liu, Qiao Wu, Weiwei Liu, Zongyin Gu, Wenjing Wang, Ping Xu, Hong Ma and Xiaochun Ge
Received: February 3, 2017         Accepted: February 28, 2017
Online Date: March 6, 2017
DOI: 10.1111/jipb.12530
   
      
    

Root organogenesis involves cell division, differentiation and expansion. The molecular mechanisms regulating root development are not fully understood. In this study, we identified poly(adenosine diphosphate (ADP)-ribose) polymerases (PARPs) as new players in root development. PARP catalyzes poly(ADP-ribosyl)ation of proteins by repeatedly adding ADP-ribose units onto proteins using nicotinamide adenine dinucleotide (NAD+) as the donor. We found that inhibition of PARP activities by 3-aminobenzomide (3-AB) increased the growth rates of both primary and lateral roots, leading to a more developed root system. The double mutant of Arabidopsis PARPs, parp1parp2, showed more rapid primary and lateral root growth. Cyclin genes regulating G1-to-S and G2-to-M transition were up-regulated upon treatment by 3-AB. The proportion of 2C cells increased while cells with higher DNA ploidy declined in the roots of treated plants, resulting in an enlarged root meristematic zone. The expression level of PARP2 was very low in the meristematic zone but high in the maturation zone, consistent with a role of PARP in inhibiting mitosis and promoting cell differentiation. Our results suggest that PARPs play an important role in root development by negatively regulating root cell division.

Abstract (Browse 107)   |   References   |   Full Text HTML   |   Full Text PDF       
  Sexual Plant Reproduction
Acetylglutamate kinase is required for both gametophyte function and embryo development in Arabidopsis thaliana
Author: Jie Huang, Dan Chen, Hailong Yan, Fei Xie, Ying Yu, Liyao Zhang, Mengxiang Sun and Xiongbo Peng
Received: February 10, 2017         Accepted: March 14, 2017
Online Date: March 15, 2017
DOI: 10.1111/jipb.12536
   
      
    

The specific functions of the genes encoding arginine biosynthesis enzymes in plants are not well characterized. We report the isolation and characterization of Arabidopsis thaliana N-acetylglutamate kinase (NAGK), which catalyzes the second step of arginine biosynthesis. NAGK is a plastid-localized protein and is expressed in most developmental processes in Arabidopsis. Heterologous expression of the Arabidopsis NAGK gene in a NAGK-deficient Escherichia coli strain fully restores bacterial growth on arginine-deficient medium. nagk mutant pollen tubes grow more slowly than wild type pollen tubes and the phenotype is restored by either specifically complementation NAGK in pollen or exogenous supplementation of arginine. nagk female gametophytes are defective in micropylar pollen tube guidance due to the fact that female gametophyte cell fate specification was specifically affected. Specific expression of NAGK in synergid cells rescues the defect of nagk female gametophytes. Loss-of-function of NAGK results in Arabidopsis embryos not developing beyond the four-celled embryo stage. The embryo-defective phenotype in nagk/NAGK plants cannot be rescued by watering nagk/NAGK plants with arginine or ornithine supplementation. In conclusion, the results reveal a novel role of NAGK and arginine in regulating gametophyte function and embryo development, and provide valuable insights into arginine transport during embryo development.

Abstract (Browse 88)   |   References   |   Full Text HTML   |   Full Text PDF       
  Molecular Physiology
A zinc finger protein, interacted with cyclophilin, affects root development via IAA pathway in rice
Author: Peng Cui, Hongbo Liu, Songlin Ruan, Basharat Ali, Rafaqat Ali Gill, Huasheng Ma, Zhifu Zheng and Weijun Zhou
Received: November 4, 2016         Accepted: February 28, 2017
Online Date: March 7, 2017
DOI: 10.1111/jipb.12531
   
      
    

The plant hormone auxin plays a crucial role in lateral root development. To better understand the molecular mechanisms underlying lateral root formation, an auxin-responsive gene OsCYP2 (Os02g0121300) was characterized from rice. Compared to the wild type, OsCYP2-RNAi (RNA interference) lines exhibited distinctive defects in lateral root development. Yeast two-hybrid and glutathione S-transferase pull-down results confirmed that OsCYP2 interacted with a C2HC-type zinc finger protein (OsZFP, Os01g0252900) which is located in the rice nucleus. T2 OsZFP-RNAi lines had significantly fewer lateral roots than did wild-type plants, which suggests a role for OsCYP2 and OsZFP in regulating lateral root development. Quantitative real-time polymerase chain reaction showed that the expression of certain Aux/IAA (auxin/indole-3-acetic acid) genes was altered in OsCYP2- and OsZFP-RNAi lines in response to IAA. These findings imply that OsCYP2 and OsZFP participate in IAA signal pathways controlling lateral root development. More importantly, OsIAA11 showed functional redundancy not only in OsCYP2-RNAi lines but also in OsZFP-RNAi lines, which provides important clues for the elucidation of mechanisms controlling lateral root development in response to auxin.

Abstract (Browse 84)   |   References   |   Full Text HTML   |   Full Text PDF       

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