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    28 July 2020, Volume 27 Issue 4 Previous Issue    Next Issue

    Letter
    Review
    Research Paper
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    Letter
    Genetic Variation Dissection of Rice Blast Resistance Using an Indica Population
    Mengchen Zhang, Zhonghua Wei, Xiaoping Yuan, Caihong Wang, Shan Wang, Xiaojun Niu, Xin Xu, Qun Xu, Yue Feng, Hanyong Yu, Yiping Wang, Zhiwei Zhu, Rongrong Zhai, Yaolong Yang, Xinghua Wei
    2020, 27(4): 255-258.  DOI: 10.1016/j.rsci.2020.05.001
    Abstract ( )   HTML ( )   PDF (520KB) ( )  
    OsPS6 Plays Important Role in Anther Development and Microspore Formation
    Weimin Zhou, Menghui Ma, Lianping Sun, Peng Zhang, Shiqiong Lv, Zhengzheng Zhong, Hanhua Tong
    2020, 27(4): 259-262.  DOI: 10.1016/j.rsci.2020.05.002
    Abstract ( )   HTML ( )   PDF (846KB) ( )  
    Review
    Strategy for Use of Rice Blast Resistance Genes in Rice Molecular Breeding
    Ning Xiao, Yunyu Wu, Aihong Li
    2020, 27(4): 263-277.  DOI: 10.1016/j.rsci.2020.05.003
    Abstract ( )   HTML ( )   PDF (1168KB) ( )  

    Rice blast is one of the most destructive diseases affecting rice production worldwide. The development and rational use of resistant varieties has been the most effective and economical measure to control blast. In this review, we summarized the cloning and utilization of rice blast resistance genes, such as Pi1, Pi2, Pi9, Pi54, Pigm and Piz-t. We concluded that three main problems in the current breeding of rice blast resistance are: availability of few R (resistance) genes that confer resistance to both seedling and panicle blast, the resistance effect of pyramided lines is not the result of a simple accumulation of resistance spectrum, and only a few R genes have been successfully used for molecular breeding. Therefore, novel utilization strategies for rice blast R genes in molecular breeding were proposed, such as accurately understanding the utilization of R genes in main modern rice varieties, creating a core resistant germplasm with excellent comprehensive traits, screening and utilizing broad- spectrum and durable resistance gene combinations. Lastly, the trends and possible development direction of blast resistance improvement were also discussed, including new genes regulating resistance identified via GWAS (genome-wide association study) and improving rice blast resistance using genetic editing.

    Deciphering Rice Lesion Mimic Mutants to Understand Molecular Network Governing Plant Immunity and Growth
    Xiaobo Zhu, Mu Ze, Mawsheng Chern, Xuewei Chen, Jing Wang
    2020, 27(4): 278-288.  DOI: 10.1016/j.rsci.2020.05.004
    Abstract ( )   HTML ( )   PDF (885KB) ( )  

    Plant lesion mimic mutants (lmms) generally possess autoimmunity and hypersensitive response (HR)-like cell death in the absence of biotic or abiotic stress. They have attracted much attention because they are useful tools for deciphering the interaction between defense signaling and growth. Recent studies have identified more than 30 lmms involved in the plant immune response and cell death in rice. Genes underlying these lmms, coding for diverse types of proteins, mainly regulate transcription, protein translation and modification, vesicular trafficking and catalyzation of metabolism. Here, we presented an overview of the most recent advances on the study of lmms in rice and proposed a perspective on potential utilization of LMM genes in agriculture.

    Research Paper
    Alternative Splicing of OsRAD1 Defines C-Terminal Domain Essential for Protein Function in Meiosis
    Shuting Yuan, Chunjue Xu, Wei Yan, Zhenyi Chang, Xingwang Deng, Zhufeng Chen, Jianxin Wu, Xiaoyan Tang
    2020, 27(4): 289-301.  DOI: 10.1016/j.rsci.2020.05.005
    Abstract ( )   HTML ( )   PDF (1497KB) ( )  

    Alternative splicing can generate multiple mRNAs that differ in their untranslated regions or coding sequences, and these differences might affect mRNA stability or result in different protein isoforms with diverse functions and/or localizations. In this study, we isolated a sterile mutant in rice with abnormal meiosis of microspore mother cells and megaspore mother cells that carried a point mutation in OsRAD1 gene. Cloning of OsRAD1 cDNAs revealed three transcript variants, named as OsRAD1.1, OsRAD1.2 and OsRAD1.3, respectively, which were derived from alternative splicing of the last intron. Proteins derived from the three transcripts were mostly identical except the difference in the very C-terminal domain. The three transcripts exhibited similar expression patterns in various tissues, but the expression level of OsRAD1.1 was the highest. Specific knockout of OsRAD1.1 led to sterility, while knockout of OsRAD1.2 and OsRAD1.3 together did not change the plant fertility. Overexpression of OsRAD1.2 and OsRAD1.3 cDNAs in OsRAD1.1-specific mutant did not complement the plant fertility. Yeast two-hybrid assay showed that OsRAD1.1, but not OsRAD1.2 and OsRAD1.3, interacted with the three other meiosis proteins OsHUS1, OsRAD9 and OsRAD17, suggesting that the C-terminal domain of OsRAD1.1 is critical for the protein function.

    RNA-Seq Study Reveals AP2-Domain-Containing Signalling Regulators Involved in Initial Imbibition of Seed Germination in Rice
    Yongqi He, Jia Zhao, Defeng Feng, Zhibo Huang, Jiaming Liang, Yufei Zheng, Jinping Cheng, Jifeng Ying, Zhoufei Wang
    2020, 27(4): 302-314.  DOI: 10.1016/j.rsci.2020.05.006
    Abstract ( )   HTML ( )   PDF (1390KB) ( )  

    A number of internal signals are required for seed germination. However, the precise signalling responses in the initial imbibition of seed germination are not yet fully understood in rice. In this study, the RNA sequencing (RNA-Seq) approach was conducted in 8 h imbibed seeds to understand the signalling responses in the initial imbibition of rice seed germination. A total of 563 differentially expressed genes (DEGs) with at least 4-fold change were identified in 8 h imbibed seeds compared to dry seeds. MapMan analysis revealed that the majority of signalling response-related DEGs were hormone- and transcription factor-related genes, in which the largest number of DEGs belong to the AP2-domain-containing regulators, and their expressions were significantly induced in the initial imbibition of seed germination in rice. Moreover, at least five AP2-domain-containing transcription factor OsDREBs were identified in the initial imbibition of rice seed germination, and the expressions of 251 DEGs were putatively regulated by OsDREBs through the dehydration-responsive element (DRE) cis-element assay. It suggested that the OsDREBs might play important roles in the regulation of initial seed imbibition in rice. The identified genes provide a valuable resource to study the signalling regulation of seed germination in the future.

    RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content, Alters Transcripts of Phytic Acid Biosynthetic Genes, and Modulates Mineral Distribution in Rice Seeds
    Karmakar Aritra, Bhattacharya Sananda, Sengupta Shinjini, Ali Nusrat, Nath Sarkar Sailendra, Datta Karabi, K. Datta Swapan
    2020, 27(4): 315-328.  DOI: 10.1016/j.rsci.2020.05.007
    Abstract ( )   HTML ( )   PDF (1059KB) ( )  

    Phytic acid is the principal storage form of phosphorus in plant seeds and an essential signalling molecule in several regulatory processes of plant development. However, it is known as an anti-nutrient compound owing to its potent chelating property. Thus, reducing the phytic acid content in crops is desirable. Studies involving regulation of MIPS and IPK1 genes to generate low phytate rice have been reported earlier. However, the functional significance of OsITPK and the effect of its down-regulation on phytic acid content and the associated pleiotropic effects on rice have not yet been investigated. In this study, tissue specific RNA interference (RNAi)-mediated down-regulation of a major ITPK homolog (OsITP5/6K-1) resulted in 46.2% decrease in phytic acid content of T2 transgenic seeds with a subsequent 3-fold enhancement in the inorganic phosphorus content. Silencing of OsITP5/6K-1 altered the transcript levels of essential phytic acid pathway genes, without significantly affecting the transcript levels of other OsITPK homologs. Furthermore, the mapping of elements through X-ray microfluorescence analysis revealed significant changes in the spatial distribution pattern and translocation of elements in low phytate seeds. Additionally, low phytate polished seeds exhibited 1.3-fold and 1.6-fold enhancement in iron and zinc content in the grain endosperm, respectively. Silencing of OsITP5/6K-1 also altered the amino acid and myo-inositol content of the transgenic seeds. Our results successfully established that RNAi-mediated silencing of OsITP5/6K-1 gene significantly reduced the phytate levels in seeds without hampering the germination potential of seeds and plant growth. The present study provided an insight into the mechanism of phytic acid biosynthesis pathway.

    Accumulation of Polyphenolic Compounds and Osmolytes under Dehydration Stress and Their Implication in Redox Regulation in Four Indigenous Aromatic Rice Cultivars
    Dey Nivedita, Bhattacharjee Soumen
    2020, 27(4): 329-344.  DOI: 10.1016/j.rsci.2020.05.008
    Abstract ( )   HTML ( )   PDF (1324KB) ( )  

    Present work was undertaken to screen some drought tolerant indigenous aromatic rice cultivars (IARCs), commonly cultivated in West Bengal, India, based on their capacity to produce osmolytes, redox-sensitive phenolic acids and flavonoids, as contrivances for redox-regulation under drought stress. Polyethylene glycol induced post imbibitional dehydration stress mediated changes in redox regulatory properties of the germinating seeds of the four IARCs (Jamainadu, Tulaipanji, Sitabhog, Badshabhog), which were assessed in terms of changes in prooxidant accumulation (in-situ localization of reactive oxygen species (ROS) by confocal microscopy, DCFDA (2′,7′-dichlorofluorescin diacetate) oxidation, O2- and H2O2 accumulation), cumulative antioxidative defense (radical scavenging property and total thiol content), ROS scavenging phenolic acids (gallic acid, protocatechuic acid, gentisic acid, para-hydroxy benzoic acid, chlorogenic acid, caffeic acid, syringic acid, salicylic acid, sinapic acid and p-coumaric acid) and flavonoids (catechin, naringin, rutin, quercetin, kaempferol, myricetin and apigenin). The capability of germinating seeds to accumulate osmolytes (like glycinebetaine, proline, soluble carbohydrates and K+ ion) and polyphenolic compounds was also correlated with their corresponding redox status and redox biomarkers (conjugated diene, hydroperoxide, thiobarbituric acid reactive substances and free carbonyl content) produced under the same conditions. The results in general showed that accumulation of osmolytes along with the redox-sensitive phenolics and flavonoids conferred the ability to maintain the redox homeostasis under drought stress for the tolerant IARCs (Badshabhog and Tulaipanji).

    Responses of Lowland, Upland and Aerobic Rice Genotypes to Water Limitation During Different Phases
    Vijayaraghavareddy Preethi, Xinyou Yin, C. Struik Paul, Makarla Udayakumar, Sreeman Sheshshayee
    2020, 27(4): 345-354.  DOI: 10.1016/j.rsci.2020.05.009
    Abstract ( )   HTML ( )   PDF (789KB) ( )  

    Rice yield reduction due to water limitation depends on its severity and duration and on the phenological stage of its occurrence. We exposed three contrasting rice genotypes, IR64, UPLRi7 and Apo (adapted to lowland, upland and aerobic conditions, respectively), to three water regimes (puddle, 100% and 60% field capacity) in pots during the vegetative (GSI), flowering (GSII) and grain filling (GSIII) stages. Stress at all the three stages significantly reduced yield especially in lowland genotype IR64. Effect of water limitation was more severe at GSII than at the other two stages. Stress at GSI stage reduced both source activity (leaf area and photosynthetic rate) and sink capacity (tiller number or panicle number per pot). When stress was imposed at GSII, spikelet fertility was most affected in all the three genotypes. In both GSII and GSIII, although leaf area was constant in all the three water regimes, estimated relative whole-plant photosynthesis was strongly associated with yield reduction. Reduced photosynthesis due to stress at any given stage was found to have direct impact on yield. Compared to the other genotypes, Apo had deeper roots and maintained a better water relation, thus, higher carbon gain and spikelet viability, and ultimately, higher biomass and productivity under water-limited conditions. Therefore, screening for these stage-dependent adaptive mechanisms is crucial in breeding for sustained rice production under water limitation.