January 2017, Volume 59 Issue 1, Pages 1每74.


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          Cell and Developmental Biology
SUMO E3 Ligases GmSIZ1a and GmSIZ1b regulate vegetative growth in soybean  
Author: Bin Cai, Xiangxiong Kong, Chao Zhong, Suli Sun, Xiao Feng Zhou, Yin Hua Jin, Youning Wang, Xia Li, Zhendong Zhu and Jing Bo Jin
Journal of Integrative Plant Biology 2017 59(1): 2每14
Published Online: October 20, 2016
DOI: 10.1111/jipb.12504
      
    

SIZ1 is a small ubiquitin-related modifier (SUMO) E3 ligase that mediates post-translational SUMO modification of target proteins and thereby regulates developmental processes and hormonal and environmental stress responses in Arabidopsis. However, the role of SUMO E3 ligases in crop plants is largely unknown. Here, we identified and characterized two Glycine max (soybean) SUMO E3 ligases, GmSIZ1a and GmSIZ1b. Expression of GmSIZ1a and GmSIZ1b was induced in response to salicylic acid (SA), heat, and dehydration treatment, but not in response to cold, abscisic acid (ABA), and NaCl treatment. Although GmSIZ1a was expressed at higher levels than GmSIZ1b, both genes encoded proteins with SUMO E3 ligase activity in vivo. Heterologous expression of GmSIZ1a or GmSIZ1b rescued the mutant phenotype of Arabidopsis siz1-2, including dwarfism, constitutively activated expression of pathogen-related genes, and ABA-sensitive seed germination. Simultaneous downregulation of GmSIZ1a and GmSIZ1b (GmSIZ1a/b) using RNA interference (RNAi)-mediated gene silencing decreased heat shock-induced SUMO conjugation in soybean. Moreover, GmSIZ1RNAi plants exhibited reduced plant height and leaf size. However, unlike Arabidopsis siz1-2 mutant plants, flowering time and SA levels were not significantly altered in GmSIZ1RNAi plants. Taken together, our results indicate that GmSIZ1a and GmSIZ1b mediate SUMO modification and positively regulate vegetative growth in soybean.

Abstract (Browse 197)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
SUMOylation is a rapid and reversible post-translational process, which affects protein-protein interactions, protein targeting, enzymatic activity and protein stability. However, the role of SUMOylation in soybean is unknown. Here, we report that two soybean SUMO E3 ligases, GmSIZ1a and GmSIZ1b, mediate SUMO modifications and positively regulate vegetative growth in soybean.
Arabidopsis SUMO protease ASP1 positively regulates flowering time partially through regulating FLC stability  
Author: Xiangxiong Kong, Xi Luo, Gao-Ping Qu, Peng Liu and Jing Bo Jin
Journal of Integrative Plant Biology 2017 59(1): 15每29
Published Online: December 7, 2016
DOI: 10.1111/jipb.12509
      
    

The initiation of flowering is tightly regulated by the endogenous and environment signals, which is crucial for the reproductive success of flowering plants. It is well known that autonomous and vernalization pathways repress transcription of FLOWERING LOCUS C (FLC), a focal floral repressor, but how its protein stability is regulated remains largely unknown. Here, we found that mutations in a novel Arabidopsis SUMO protease 1 (ASP1) resulted in a strong late-flowering phenotype under long-days, but to a lesser extent under short-days. ASP1 localizes in the nucleus and exhibited a SUMO protease activity in vitro and in vivo. The conserved Cys-577 in ASP1 is critical for its enzymatic activity, as well as its physiological function in the regulation of flowering time. Genetic and gene expression analyses demonstrated that ASP1 promotes transcription of positive regulators of flowering, such as FT, SOC1 and FD, and may function in both CO-dependent photoperiod pathway and FLC-dependent pathways. Although the transcription level of FLC was not affected in the loss-of-function asp1 mutant, the protein stability of FLC was increased in the asp1 mutant. Taken together, this study identified a novel bona fide SUMO protease, ASP1, which positively regulates transition to flowering at least partly by repressing FLC protein stability.

Abstract (Browse 129)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
SUMOylation is a rapid post-translational modification, which can be reversed by SUMO proteases. Arabidopsis contains more than 60 putative SUMO proteases, but their biological functions remain largely unknown. This study identified a novel SUMO protease, ASP1, which positively regulate transition to flowering partly by repressing FLC protein stability.
ARF2 coordinates with PLETHORAs and PINs to orchestrate ABA-mediated root meristem activity in Arabidopsis  
Author: Sujittra Promchuea, Yujuan Zhu, Zhizhong Chen, Jing Zhang and Zhizhong Gong
Journal of Integrative Plant Biology 2017 59(1): 30每43
Published Online: November 7, 2016
DOI: 10.1111/jipb.12506
      
    

Multiple hormones, including abscisic acid (ABA) and auxin, regulate cell division and differentiation of Arabidopsis root meristems. AUXIN RESPONSE FACTOR 2 (ARF2) functions as a negative regulator of ABA responses, as seed germination and primary root growth of arf2 mutants are hypersensitive to ABA. In this study, we found that ABA treatment reduced the expression levels of the PIN-FORMEDs (PIN) auxin efflux carriers, PIN1, PIN3, PIN4, and PIN7, to a greater extent in the root meristems of arf2-101 mutant than in the wild type. Also, arf2-101 pin1 and arf2-101 pin4 double mutants show less ABA-induced inhibition of root meristem activity than the arf2-101 mutants. Furthermore, ARF2 positively mediates the transcripts of transcription factor PLETHORA 1 (PLT1) gene but negatively mediates PLT2 at protein level in root meristems. Using a dexamethasone (DEX)-inducible transgenic line, Pro35S:PLT2-GR, we showed that PLT2 greatly promotes cell division and completely inhibits cell differentiation in root meristems of the arf2-101 mutant once PLT2 is induced by DEX, which can be partially reversed by ABA treatment, suggesting that ABA regulates root meristem activity in both ARF2-dependent and independent pathways. Our results uncover a complex regulatory architecture in which ARF2 coordinates with PLTs and PINs to orchestrate ABA-mediated regulation of root meristem activity in Arabidopsis.

Abstract (Browse 492)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
PLETHORA 1 (PLT1) and PLT2 are two key transcription factors that regulate the root apical meristem. It is found that AUXIN RESPONSE FACTOR2 (ARF2) negatively mediates stability of PLT2 protein. Conditional overexpression of PLT2 largely promotes cell division and completely inhibits cell differentiation in root meristems of the arf2 mutant.
          Molecular Ecology and Evolution
Sex ratio of mirid populations shifts in response to hostplant co-infestation or altered cytokinin signaling  
Author: Nora Adam, Theresa Erler, Mario Kallenbach, Martin Kaltenpoth, Grit Kunert, Ian T. Baldwin and Meredith C. Schuman
Journal of Integrative Plant Biology 2017 59(1): 44每59
Published Online: November 14, 2016
DOI: 10.1111/jipb.12507
      
    

Herbivore species sharing a host plant often compete. In this study, we show that host plant-mediated interaction between two insect herbivores − a generalist and a specialist − results in a sex ratio shift of the specialist's offspring. We studied demographic parameters of the specialist Tupiocoris notatus (Hemiptera: Miridae) when co-infesting the host plant Nicotiana attenuata (Solanaceae) with the generalist leafhopper Empoasca sp. (Hemiptera: Cicadellidae). We show that the usually female-biased sex ratio of T. notatus shifts toward a higher male proportion in the offspring on plants co-infested by Empoasca sp. This sex ratio change did not occur after oviposition, nor is it due differential mortality of female and male nymphs. Based on pyrosequencing and PCR of bacterial 16S rRNA amplicons, we concluded that sex ratio shifts were unlikely to be due to infection with Wolbachia or other known sex ratio-distorting endosymbionts. Finally, we used transgenic lines of N. attenuata to evaluate if the sex ratio shift could be mediated by changes in general or specialized host plant metabolites. We found that the sex ratio shift occurred on plants deficient in two cytokinin receptors (irCHK2/3). Thus, cytokinin-regulated traits can alter the offspring sex ratio of the specialist T. notatus.

Abstract (Browse 408)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The specialist herbivore T. notatus usually has a female-biased sex ratio on N. attenuata plants. When plants are co-infested with the generalist Empoasca sp., the sex ratio of T. notatus progeny becomes more male-biased. Similar affects were observed without Empoasca sp. co-infestation on plants deficient in two cytokinin receptors.
          New Resources
Development and utilization of a new chemically-induced soybean library with a high mutation density  
Author: Zhongfeng Li, Lingxue Jiang, Yansong Ma, Zhongyan Wei, Huilong Hong, Zhangxiong Liu, Jinhui Lei, Ying Liu, Rongxia Guan, Yong Guo, Longguo Jin, Lijuan Zhang, Yinghui Li, Yulong Ren, Wei He, Ming Liu, Nang Myint Phyu Sin Htwe, Lin Liu, Bingfu Guo, Jian Song, Bing Tan, Guifeng Liu, Maiquan Li, Xianli Zhang, Bo Liu, Xuehui Shi, Sining Han, Sunan Hua, Fulai Zhou, Lili Yu, Yanfei Li, Shuang Wang, Jun Wang, Ruzhen Chang and Lijuan Qiu
Journal of Integrative Plant Biology 2017 59(1): 60每74
Published Online: October 24, 2016
DOI: 10.1111/jipb.12505
      
    

Mutagenized populations have provided important materials for introducing variation and identifying gene function in plants. In this study, an ethyl methanesulfonate (EMS)-induced soybean (Glycine max) population, consisting of 21,600 independent M2 lines, was developed. Over 1,000 M4 (5) families, with diverse abnormal phenotypes for seed composition, seed shape, plant morphology and maturity that are stably expressed across different environments and generations were identified. Phenotypic analysis of the population led to the identification of a yellow pigmentation mutant, gyl, that displayed significantly decreased chlorophyll (Chl) content and abnormal chloroplast development. Sequence analysis showed that gyl is allelic to MinnGold, where a different single nucleotide polymorphism variation in the Mg-chelatase subunit gene (ChlI1a) results in golden yellow leaves. A cleaved amplified polymorphic sequence marker was developed and may be applied to marker-assisted selection for the golden yellow phenotype in soybean breeding. We show that the newly developed soybean EMS mutant population has potential for functional genomics research and genetic improvement in soybean.

Abstract (Browse 176)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
A new ethyl methanesulfonate (EMS) -induced soybean (Glycine max) population was developed. Over one thousand mutants with diverse abnormal phenotypes across generations and environments were identified and stored in the National GenBank. Our study shows that the mutants have big potential for accelerating functional genomic research and genetic improvement in soybean.
 

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