November 2016, Volume 58 Issue 11, Pages 873每940.


Cover Caption: Lipidomics in Arabidopsis
Lipids function both as membrane components and signaling molecules in plants and animals. In the paper of Wang et al (890每902), a large set of phospholipid species is identified from Arabidopsis seedlings through lipidomic studies. The study also reveals a dynamics change of distinct phospholipids during seedling growth, suggesting a crucial role of phospholipids in plant development.

 

          Cell and Developmental Biology
Overexpression of INCREASED CAMBIAL ACTIVITY, a putative methyltransferase, increases cambial activity and plant growth  
Author: Hyunsook Kim, Mikiko Kojima, Daeseok Choi, Soyoung Park, Minami Matsui, Hitoshi Sakakibara and Ildoo Hwang
Journal of Integrative Plant Biology 2016 58(11): 874每889
Published Online: June 20, 2016
DOI: 10.1111/jipb.12486
      
    

Cambial activity is a prerequisite for secondary growth in plants; however, regulatory factors controlling the activity of the secondary meristem in radial growth remain elusive. Here, we identified INCREASED CAMBIAL ACTIVITY (ICA), a gene encoding a putative pectin methyltransferase, which could function as a modulator for the meristematic activity of fascicular and interfascicular cambium in Arabidopsis. An overexpressing transgenic line, 35S::ICA, showed accelerated stem elongation and radial thickening, resulting in increased accumulation of biomass, and increased levels of cytokinins (CKs) and gibberellins (GAs). Expression of genes encoding pectin methylesterases involved in pectin modification together with pectin methyltransferases was highly induced in 35S::ICA, which might contribute to an increase of methanol emission as a byproduct in 35S::ICA. Methanol treatment induced the expression of GA- or CK-responsive genes and stimulated plant growth. Overall, we propose that ectopic expression of ICA increases cambial activity by regulating CK and GA homeostasis, and methanol emission, eventually leading to stem elongation and radial growth in the inflorescence stem.

Abstract (Browse 835)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The vascular cambium has a remarkable potential to initiate radial thickening of secondary growth to provide biomass, a renewable and sustainable source of bioenergy. This study proposed that INCREASED CAMBIAL ACTIVITY (ICA), a gene encoding a putative pectin methyltransferase, controls cambial activity in Arabidopsis by regulating CK and GA homeostasis and methanol emission.
          Metabolism and Biochemistry
Lipidomic profiling analysis reveals the dynamics of phospholipid molecules in Arabidopsis thaliana seedling growth
Author: Yi-Sheng Wang, Hong-Yan Yao and Hong-Wei Xue
Journal of Integrative Plant Biology 2016 58(11): 890每902
Published Online: March 26, 2016
DOI: 10.1111/jipb.12481
      
    

High-throughput lipidomic profiling provides a sensitive approach for discovering minor lipid species. By using an advance in electrospray ionization tandem mass spectrometry, a large set of phospholipid molecular species (126 species) with high resolution were identified from Arabidopsis seedling; of them 31 species are newly identified (16 are unique in plants), including 13 species of phosphatidic acid (PA), nine phosphatidylcholine, six phosphatidylinositol and three phosphatidylserine. Further analysis of the lipidomic profile reveals dynamics of phospholipids and distinct species alterations during seedling development. PA molecules are found at the lowest levels in imbibition and follow an increasing trend during seedling growth, while phosphatidylethanolamine (PE) molecules show the opposite pattern with highest levels at imbibition and a general decreasing trend at later stages. Of PA molecular species, 34:2-, 34:3-, 36:4-, 36:5-, 38:3- and 38:4-PA increase during radicle emergence, and 34:2- and 34:3-PA reach highest levels during hypocotyl and cotyledon emergence from the seed coat. Conversely, molecular species of PE show higher levels in imbibition and decrease in later stages. These results suggest the crucial roles of specific molecular species and homeostasis of phospholipid molecules in seedling growth and provide insights into the mechanisms of how phospholipid molecules are involved in regulating plant development.

Abstract (Browse 407)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
By using lipidomic profiling analysis with an advance in electrospray ionization tandem mass spectrometry, we identified a large set of phospholipid molecular species (126 species) from Arabidopsis, which revealed the dynamics of phospholipid molecules in seedling growth. Our results provided the insights into the mechanisms of phospholipid molecules regulating plant development.
          Molecular Ecology and Evolution
Molecular evidence for biochemical diversification of phenolamide biosynthesis in rice plants
Author: Kimiaki Tanabe, Yuko Hojo, Tomonori Shinya and Ivan Galis
Journal of Integrative Plant Biology 2016 58(11): 903每913
Published Online: March 26, 2016
DOI: 10.1111/jipb.12480
      
    

Two phenolamides (PAs), p-coumaroylputrescine and feruloylputrescine strongly accumulate in rice (Oryza sativa cv. Nipponbare) leaves subjected to attack of chewing and sucking herbivores. Here we identified and characterized in vitro three novel rice genes that mediated coumaroyl-CoA/feruloyl-CoA conjugation to polyamines, putrescine and agmatine. Interestingly, two genes were highly specific for their polyamine substrates, encoding putrescine N-hydroxycinnamoyltransferase and agmatine N-hydroxycinnamoyltransferase, while the third enzyme could use both polyamines and it was therefore annotated as putrescine/agmatine N-hydroxycinnamoyltransferase. All genes were preferentially expressed in rice roots and developing flowers, and in addition, the putrescine/agmatine N-hydroxycinnamoyltransferase transcripts were strongly induced by wounding in the young rice leaves. Because the wound response of this gene was only partially suppressed in the jasmonoyl-L-isoleucine deficient plants (Osjar1), it suggests that its upregulation (as well as inducible PAs in rice) may be largely independent of jasmonoyl-L-isoleucine signaling pathway. The finding of three closely related genes with a similar and/or overlapping activity in PA biosynthesis provides another striking example of rapid diversification of plant metabolism in response to environmental stresses in nature.

Abstract (Browse 516)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Phenolamides are compounds with multiple defense roles in plants. We identified three structurally related genes with a similar and/or overlapping activity in phenolamide biosynthesis in rice. Our findings thus illustrate rapid diversification of plant metabolism in response to herbivory and other biotic stresses in nature.
          Plant-environmental Interactions
Wheat ear carbon assimilation and nitrogen remobilization contribute significantly to grain yield  
Author: Bangwei Zhou, Maria Dolores Serret, Abdelhalim Elazab, Jordi Bort Pie,José Luis Araus, Iker Aranjuelo and Álvaro Sanz-Sáez
Journal of Integrative Plant Biology 2016 58(11): 914每926
Published Online: March 18, 2016
DOI: 10.1111/jipb.12478
      
    

The role of wheat ears as a source of nitrogen (N) and carbon (C) in the grain filling process has barely been studied. To resolve this question, five wheat genotypes were labeled with 15N-enriched nutrient solution. N remobilization and absorption were estimated via the nitrogen isotope composition of total organic matter and Rubisco. Gas exchange analyses showed that ear photosynthesis contributed substantially to grain filling in spite of the great loss of C due to respiration. Of the total kernel N, 64.7% was derived from the N acquired between sowing and anthesis, while the remaining 35.3% was derived from the N acquired between anthesis and maturity. In addition, 1.87 times more N was remobilized to the developing kernel from the ear than from the flag leaf. The higher yielding genotypes showed an increased N remobilization to the kernel compared to the lower yielding genotypes. In addition, the higher yielding genotypes remobilized more N from the ears to the kernel than the lower yielding genotypes, while the lower yielding genotypes remobilized more N from the flag leaf to the kernel. Therefore, the ears contribute significantly toward fulfilling C and N demands during grain filling.

Abstract (Browse 937)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This study demonstrated that wheat's ear play a more important role in carbon (C) assimilation and nitrogen (N) remobilization to grain, than it has been stated before. Our study also validated that 15N labelling is a useful tool to study N remobilization in wheat.
          Plant Reproduction Biology
MARIS plays important roles in Arabidopsis pollen tube and root hair growth
Author: Hong-Ze Liao, Meng-Meng Zhu, Hong-Hui Cui, Xin-Yu Du, Yu Tang, Li-Qun Chen, De Ye and Xue-Qin Zhang
Journal of Integrative Plant Biology 2016 58(11): 927每940
Published Online: May 23, 2016
DOI: 10.1111/jipb.12484
      
    

In flowering plants, male gametes are delivered to female gametes for double fertilization through pollen tubes. Therefore, pollen tube growth is crucial for double fertilization. Despite its importance to sexual reproduction, genetic mechanisms of pollen tube growth remain poorly understood. In this study, we characterized the receptor-like cytoplasmic protein kinase (RLCK) gene, MARIS (MRI) that plays critical roles in pollen tube growth. MRI is preferentially expressed in pollen grains, pollen tubes and roots. Mutation in MRI by a Ds insertion led to a burst of pollen tubes after pollen germination. Pollen-rescue assay by pollen and pollen tube-specific expression of MRI in the mri-4 mutant showed that loss of MRI function also severely affected root hair elongation. MRI protein interacted with the protein kinase OXIDATIVE SIGNAL INDUCIBLE1 (OXI1) in the in vitro and in vivo assays, which functions in plant defence and root hair development, and was phosphorylated by OXI1 in vitro. Our results suggest that MRI plays important roles in pollen tube growth and may function in root hair elongation through interaction with OXI1.

Abstract (Browse 422)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Mutation in MRI caused rupture in pollen tube and inhibited the growth in root hair. Therefore, MRI is essential for polar growth in Arabidopsis thaliana.
 

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