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28 January 2021, Volume 28 Issue 1 Previous Issue    Next Issue
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WRKY72 Negatively Regulates Seed Germination Through Interfering Gibberellin Pathway in Rice Huimei Wang, Yuxuan Hou, Shuang Wang, Xiaohong Tong, Liqun Tang, Adijat Ajadi Abolore, Jian Zhang, Yifeng Wang 2021, 28(1): 1-5.  DOI: 10.1016/j.rsci.2020.11.001 Abstract ( )   HTML ( )   PDF (751KB) ( )

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A New PCR/LDR-Based Multiplex Functional Molecular Marker for Marker-Assisted Breeding in Rice Huangwei Chu, Rongjian Tu, Fuan Niu, Jihua Zhou, Bin Sun, Zhongyong Luo, Can Cheng, Liming Cao 2021, 28(1): 6-10.  DOI: 10.1016/j.rsci.2020.11.002 Abstract ( )   HTML ( )   PDF (524KB) ( )

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Different Hypotheses for Resistance Loss of Rice Varieties to Magnaporthe oryzae Kehan Zhao, Shiwen Huang 2021, 28(1): 11-12.  DOI: 10.1016/j.rsci.2020.11.003 Abstract ( )   HTML ( )   PDF (380KB) ( )

Review

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Anticancer Activities of Plant Secondary Metabolites: Rice Callus Suspension Culture as a New Paradigm Ramakrishna Wusirika, Kumari Anuradha, Rahman Nafeesa, Mandave Pallavi 2021, 28(1): 13-30.  DOI: 10.1016/j.rsci.2020.11.004 Abstract ( )   HTML ( )   PDF (1032KB) ( )   Plant natural products including alkaloids, polyphenols, terpenoids and flavonoids have been reported to exert anticancer activity by targeting various metabolic pathways. The biological pathways regulated by plant products can serve as novel drug targets. Plant natural compounds or their derivatives used for cancer treatment and some novel plant-based compounds which are used in clinical trials were discussed. Callus suspension culture with secondary metabolites can provide a continuous source of plant pharmaceuticals without time and space limitations. Previous research has shown that rice callus suspension culture can kill > 95% cancer cells with no significant effect on the growth of normal cells. The role of candidate genes and metabolites which are likely to be involved in the process and their potential to serve as anticancer and anti-inflammatory agents were discussed. Large scale production of plant callus suspension culture and its constituents can be achieved using elicitors which enhance specific secondary metabolites combined with bioprocess technology.

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Physiochemical Properties of Resistant Starch and Its Enhancement Approaches in Rice Yi Ding, Maike Wang, Yi Shen, Xiaoli Shu, Dianxing Wu, Wenjian Song 2021, 28(1): 31-42.  DOI: 10.1016/j.rsci.2020.11.005 Abstract ( )   HTML ( )   PDF (873KB) ( )   With changes in food preferences and life styles, more and more attentions have been focused on healthier food. Nowadays, resistant starch (RS) which can resist digestion in the human intestine has been recognized and accepted. High RS diet shows great benefit for the human health, and breeding high RS rice variety is a great target for realizing dietary intervention. To provide guidance for RS improvement in rice, this review summarized the unique physiochemical properties of RS and the possible approaches, i.e. genetic regulation, for enhancing RS content in rice, and proposed the potential ways to obtain rice variety with high RS content.

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Flooding Tolerance in Rice: Focus on Mechanisms and Approaches Panda Debabrata, Barik Jijnasa 2021, 28(1): 43-57.  DOI: 10.1016/j.rsci.2020.11.006 Abstract ( )   HTML ( )   PDF (826KB) ( )   Flooding is one of the most hazardous natural disasters and a major stress constraint to rice production throughout the world, which results in huge economic loss. Approximately one-fourth of the global rice crops (approximately 40 million hectares) are grown in rainfed lowland plots that are prone to seasonal flooding. A great progress has been made during last two decades in our understanding of the mechanisms involved in adaptation and tolerance to flooding/submergence in rice. In this review, we summarized the physiological and molecular mechanisms that contribute to tolerance of flooding/ submergence in rice. We also covered various features of flooding stress with special reference to rice plants, viz. different types of flooding stress, environmental characterisation of flood water, impact of flooding stress on rice plant and their morphological, physiological and metabolic responses under flooding. A brief discussion on the tolerance mechanism in rice exhibited to different types of flooding will be focused for the future crop improvement programme for development of flooding tolerant rice variety.

Research Papers

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Genetic and Geographic Patterns of Duplicate DPL Genes Causing Genetic Incompatibility Within Rice: Implications for Multiple Domestication Events in Rice Xun Xu, Song Ge, Fumin Zhang 2021, 28(1): 58-68.  DOI: 10.1016/j.rsci.2020.11.007 Abstract ( )   HTML ( )   PDF (971KB) ( )   Strong genetic incompatibilities exist between two primary rice subspecies, indica and japonica. However, the wild ancestors of rice, O. nivara Sharma et Shastry and O. rufipogon Griff., are genetically compatible. How this genetic incompatibility became established has not been clearly elucidated. To provide insights into the process, we analyzed a pair of hybrid sterility genes in rice, DOPPELGANGER 1 (DPL1) and DOPPELGANGER 2 (DPL2). Either of the two loci can have one defective allele (DPL1- and DPL2-). Hybrid pollen carrying both DPL1- and DPL2- alleles is sterile. To explore the origination of DPL1- and DPL2-, we sequenced the DPL1 and DPL2 genes of 811 individual plants, including Oryza sativa (132), O. nivara (296) and O. rufipogon (383). We then obtained 20 DPL1 and 34 DPL2 sequences of O. sativa from online databases. Using these sequences, we analyzed the genetic and geographic distribution patterns of DPL genes in modern rice and its wild ancestors. Compared with the ancestral populations, DPL1- and DPL2- showed reduced diversity but increased frequency in modern rice. We speculated that the diversity reduction was due to a historic genetic bottleneck, and the frequency had likely increased because the defective alleles were preferred following this artificial selection. Such results indicated that standing variances in ancestral lines can lead to severe incompatibilities among descendants. Haplotype analysis indicated that the DPL1- haplotype of rice emerged from an O. nivara population in India, whereas the DPL2- haplotype emerged from O. rufipogon in South China. Hence, the evolutionary history of DPLs conforms to the presumed multiple domestication events of modern rice.

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Visualizing Meiotic Chromosome Pairing and Segregation in Interspecific Hybrids of Rice by Genomic in situ Hybridization Mao-Sen Liu, Shih-Hsuan Tseng, Ting-Chu Chen, Mei-Chu Chung 2021, 28(1): 69-80.  DOI: 10.1016/j.rsci.2020.11.008 Abstract ( )   HTML ( )   PDF (1335KB) ( )   Meiotic disturbances in F1 hybrids and their progenies are still major problems in wide hybridization. To investigate the genome affinity reflected in chromosome pairing and segregation, we studied chromosome behaviors during meiosis in two interspecific F1 hybrids [O. minuta × O. australiensis (Om × Oa, BCE genome) and Oa × O. ridleyi (Or, EHJ genome)] by using both traditional staining methods and genomic in situ hybridization (GISH). GISH analysis has been successfully performed on mitotic chromosomes to distinguish different Oryza genomes, but relatively fewer systematic analyses of meiotic chromosomes of interspecific hybrids have been reported. In the hybrids, highly irregular chromosome behaviors through meiosis resulted in producing microspores with unbalanced genome. At diakinesis of these two hybrids, most chromosomes present as univalent, with low frequency as bivalents and occasionally as trivalents. In a pollen mother cell, 2 to 8 bivalents and 0 to 4 trivalents were observed in the hybrid Oa × Or, and 1 to 8 bivalents and 0 to 5 trivalents were observed in the hybrid Om × Oa. GISH results indicated that 51.52% bivalents in Oa × Or and 79.65% bivalents in Om × Oa involved allosyndetic association, which indicates that recombination and introgression should be possible if viable backcrosses can be recovered even from triploid hybrids. In this study, we revealed that the meiotic disturbance due to low affinities between parental genomes is the major reason for the sterility of these two triploid interspecific hybrids. The two hybrids showing vigor in reproductive growth are potential genetic resources in future breeding programs. A better understanding of genomic affinities between these distant Oryza species can facilitate planning an effective breeding program by using wide hybridization, and efficient and routine GISH analysis is helpful to monitor alien introgression in the process.

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Identification of QTLs for Cadmium Tolerance During Seedling Stage and Validation of qCDSL1 in Rice Shilin Ding, Chaolei Liu, Lianguang Shang, Shenglong Yang, Anpeng Zhang, Hongzhen Jiang, Banpu Ruan, Guonan Fang, Biao Tian, Guoyou Ye, Longbiao Guo, Qian Qian, Zhenyu Gao 2021, 28(1): 81-88.  DOI: 10.1016/j.rsci.2020.11.009 Abstract ( )   HTML ( )   PDF (686KB) ( )   Cadmium (Cd) is a non-essential toxic metal that is harmful to plants. To investigate the genetic mechanism of Cd tolerance in rice, quantitative trait loci (QTLs) associated with Cd tolerance at the seedling stage were analyzed using a recombinant inbred line (RIL) population derived from a cross between PA64s and 93-11. A total of 36 QTLs associated with shoot length, root length, shoot dry weight, root dry weight and total dry weight were detected in Hangzhou and Lingshui of China. Among them, 15 QTLs were identified under the control condition and 15 QTLs were identified under the Cd stress condition, and 6 QTLs for Cd tolerant coefficient were detected on chromosomes 1, 3, 7 and 9. The qCDSL1.1 and qCDSL1.2 were identified in Hangzhou and Lingshui, respectively, and had overlapping intervals on chromosome 1. To further confirm the effects of qCDSL1.1 and qCDSL1.2, we developed a chromosome segment substitution line (CSSL), CSSLqCDSL1, in 93-11 background harboring qCDSL1.1/ qCDSL1.2 from PA64s. Compared to 93-11, CSSLqCDSL1 had increased shoot length under the Cd stress condition. These results pave the way for further isolation of those genes controlling Cd tolerance in rice and marker-assistant selection of rice elite varieties with Cd tolerance.

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Marker-Assisted Breeding of Thermo-Sensitive Genic Male Sterile Line 1892S for Disease Resistance and Submergence Tolerance Yanchang Luo, Tingchen Ma, Teo Joanne, Zhixiang Luo, Zefu Li, Jianbo Yang, Zhongchao Yin 2021, 28(1): 89-98.  DOI: 10.1016/j.rsci.2020.11.010 Abstract ( )   HTML ( )   PDF (944KB) ( )   Rice line 1892S is an elite thermo-sensitive genic male sterile (TGMS) line for two-line hybrid rice production. However, 1892S is susceptible to rice blast, bacterial blight and submergence. Here we reported the introduction of blast resistance (R) gene Pi9, bacterial blight R gene Xa21 and submergence tolerance gene Sub1A into 1892S genetic background through backcrossing and marker-assisted selection. The improved TGMS line 31892S and its hybrids conferred disease resistance to rice blast and bacterial blight, and showed submergence tolerance for over 14 d without significant loss of viability. The sterility- fertility conversion of 31892S was similar to that of 1892S. 31892S and its derived hybrid rice had similar agronomic traits and grain quality with 1892S and the control hybrid rice, respectively. The newly developed 31892S provided an improved TGMS line for two-line hybrid rice production with disease resistance to rice blast and bacterial blight, and submergence tolerance with no yield penalty or change in grain quality.

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Development of Heat Tolerant Two-Line Hybrid Rice Restorer Line Carrying Dominant Locus of OsHTAS Jan Mehmood, Shah Gulmeena, Yuqing Huang, Xuejiao Liu, Peng Zheng, Hao Du, Hao Chen, Jumin Tu 2021, 28(1): 99-108.  DOI: 10.1016/j.rsci.2020.11.011 Abstract ( )   HTML ( )   PDF (875KB) ( )   In order to create novel germplasm resources for breeding heat tolerant variety, we transferred a dominant allele OsHTAS, previously characterized and cloned from a high-temperature tolerant local variety HT54, which was collected from the rice production area of southern China, into a high- temperature sensitive intermediate breeding line HT13 through six rounds of successive backcross by using marker-assisted selection. The molecular analysis showed that the recovery of genetic background of a resultant near isogenic line (NIL), MHT13, was around 99.8%. The OsHTAS gene introduced in the MHT13 expressed normally in the HT13 genetic background, mediating heat tolerance and phenotype similar to those of the donor parent HT54. The major agronomic traits of MHT13 resembled those of the recurrent parent HT13. Moreover, MHT13 had high general combining ability and its rice quality reached the grade 3 standard of edible high-quality rice issued by Ministry of Agriculture of the People’s Republic of China, which greatly improved its application value in rice production.