Genetic Introgression Between Different Groups Reveals the Differential Process of Asian cultivated Rice

Genetic introgression plays an important role in the domestication of crops. The Asian cultivate rice consists of two major subspecies, they are indica and japonica. There are already many reports about existence of genetic introgression between the two subspecies. However, those studies often use few limited markers to characterize the genetic introgression that exists in some specific small populations. In this study we use the genome wide variation data of Asia cultivated rice to investigate their genetic introgression on the whole genome level. We detect a total of 13 significantly high introgression loci between the tropical japonica and indica population. Two different methods are used to identify the genetic introgression regions. For most of the detected introgression regions they generally get consistent results. Some previous known introgression genes are detected in the identified introgression loci, such as heat resistance gene TT1 and GLW7. The biological functions for these genetic introgression regions are annotated by the published QTL mapping results. We find that genetic introgression plays an important role in both the determination of the phenotype and the domestication process of different groups. Our study also provides useful information and resources for the study of rice gene function and domestication process.

Silencing an E3 Ubiquitin Ligase Gene OsJMJ715 Enhances the Resistance of Rice to a Piercing-Sucking Herbivore by Activating ABA and JA Signaling Pathways

The RING-type E3 ubiquitin ligases play an important role in plant growth, development, and defense responses to abiotic stresses and pathogens. However, their roles in the resistance of plants to herbivorous insects remain largely unknown. In this study, we isolated the rice gene OsJMJ715, which encodes a RING-domain containing protein, and investigated its role in rice resistance to brown planthopper (BPH, Nilaparvata lugens). OsJMJ715 is a nucleus-localized E3 ligase whose mRNA levels were upregulated by the infestation of gravid BPH females, mechanical wounding, and treatment with JA or ABA. Silencing OsJMJ715 enhanced BPH-elicited levels of ABA, JA, and JA-Ile as well as the amount of callose deposition in plants, which in turn increased the resistance of rice to BPH by reducing the feeding of BPH and the hatching rate of BPH eggs. These findings suggest that OsJMJ715 negative regulates the BPH-induced biosynthesis of ABA, JA, and JA-Ile and that BPH benefits by enhancing the expression of OsJMJ715.

Overexpression of NtSOS2 From Halophyte Plant N. tangutorum Enhances Tolerance to Salt Stress in Arabidopsis

The Salt Overly Sensitive (SOS) signaling pathway is key in responding to salt stress in plants. SOS2, a central factor in this pathway, has been studied in non-halophytes such as Arabidopsis and rice, but has so far not been reported in the halophyte Nitraria tangutorum. In order to better understand how Nitraria tangutorum acquires its tolerance for a high salt environment, here, the NtSOS2 was cloned from Nitraria tangutorum, phylogenetic analyses showed that NtSOS2 is homologous to the SOS2 of Arabidopsis and rice. Gene expression profile analysis showed that NtSOS2 localizes to the cytoplasm and cell membrane and it can be induced by salt stress. Transgenesis experiments showed that exogenous expression of NtSOS2 reduces leaf mortality and improves the germination rate, biomass and root growth of Arabidopsis under salt stress. Also, exogenous expression of NtSOS2 affected the expression of ion transporter-related genes and can rescue the phenotype of sos2-1 under salt stress. All these results revealed that NtSOS2 plays an important role in plant salt stress tolerance. Our findings will be of great significance to further understand the mechanism of salt tolerance and to develop and utilize molecular knowledge gained from halophytes to improve the ecological environment.

Assessment of Genetic Variability and Correlation of Yield Components of Elite Rice Genotypes (Oryza sativa L.)

The study was conducted to evaluate the extent of variability among the elite rice (Oryza sativa L.) genotypes for yield and yield components. Sixteen elite rice genotypes were evaluated for yield and yield contributing characters in Bangladesh Rice Research Institute, Regional Station, Satkhira. Highest grain yield (t ha-1) was observed in BR(Bio)8333-BC5-2-16, which was followed by BR16, BRRI dhan28, BRRI dhan58 and BRRI dhan29. BR7671-37-2-2-37-3-P3 had the highest number of grains per panicle with minimum thousand grain weight. Correlation analysis revealed that the number of panicles per plant (0.301), days to 50% flowering (0.606) and grain yield per plant (0.393) had the significantly positive contribution to grain yield. After evaluation of yield components, four genotypes namely BR(Bio)8333-BC5-1-20, BR(Bio)8333-BC5-2-16, BR(Bio)8333- BC5-2-22 and BR(Bio)8333-BC5-3-10 were selected as outstanding genotypes, which can be used as potential breeding materials for variety development or in the crossing program to enrich the rice gene pool in Bangladesh. Bangladesh Rice J. 24 (1): 21-29, 2020

Plasma membrane H+-ATPase overexpression increases rice yield via simultaneous enhancement of nutrient uptake and photosynthesis

Nitrogen (N) and carbon (C) are essential elements for plant growth and crop yield. Thus, improved N and C utilisation contributes to agricultural productivity and reduces the need for fertilisation. In the present study, we find that overexpression of a single rice gene, Oryza sativa plasma membrane (PM) H+-ATPase 1 (OSA1), facilitates ammonium absorption and assimilation in roots and enhanced light-induced stomatal opening with higher photosynthesis rate in leaves. As a result, OSA1 overexpression in rice plants causes a 33% increase in grain yield and a 46% increase in N use efficiency overall. As PM H+-ATPase is highly conserved in plants, these findings indicate that the manipulation of PM H+-ATPase could cooperatively improve N and C utilisation, potentially providing a vital tool for food security and sustainable agriculture.