With the intensification of the greenhouse effect, a series of natural phenomena, such as global warming, are gradually recognized; when the ambient temperature increases to the extent that it causes heat stress in plants, agricultural production will inevitably be affected. Therefore, several issues associated with heat stress in crops urgently need to be solved. Rice is one of the momentous food crops for humans, widely planted in tropical and subtropical monsoon regions. It is prone to high temperature stress in summer, leading to a decrease in yield and quality. Understanding how rice can tolerate heat stress through genetic effects is particularly vital. This article reviews how rice respond to rising temperature by integrating the molecular regulatory pathways and introduce its physiological mechanisms of tolerance to heat stress from the perspective of molecular biology. In addition, genome selection and genetic engineering for rice heat tolerance were emphasized to provide a theoretical basis for the sustainability and stability of crop yield-quality structures under high temperatures from the point of view of molecular breeding.

qRT-PCR is one of the widely used methods for analysing the expression levels of specific genes, which requires reliable experimental results with the aid of stably-expressed reference genes. Although there are some common housekeeping genes, many experiments have proved that the expression of these genes can change under different experimental conditions. Heat stress is one of the key factors affecting rice yield and quality, and there are relatively few reports of reference genes that can be used for heat stress research. To find the reference genes that can be stably expressed under heat stress, this experiment analysed 10 common reference genes and 10 new candidate genes by qRT-PCR to explore their expression patterns in rice heat-tolerant variety HT54 and heat-sensitive variety HT13 under heat stress conditions, and used GeNorm, NormFinder, BestKeeper, Delta CT and RefFinder to evaluate the expression stability of these genes. The results showed that LOC_Os06g23160, b-TUB and eIF-4a were the most stably expressed genes in HT13 and combined analysis of these three reference genes are recommended to be used for qRT-PCR normalisation. Our results also showed that LOC_Os06g23160 was an excellent reference gene more stable than common reference genes such as 18S RNA in both HT13 and HT54.

Global climate change has led to the frequent occurrence of extreme weather, in which extreme high temperature has increasingly become one of the main limiting factors affecting plant growth. High temperature causes stunted plant growth or even death, which seriously threatens agriculture, especially the production of grain crops such as rice. With the rise of global population, the demand for food continues to expand. If effective ways or methods cannot be developed to deal with the frequent high temperature stress, global food security will face a huge threat. This review introduced the main pathways and response mechanisms for plants to perceive changes in external temperature, and discussed the main pathways and regulatory mechanisms for plants to maintain their own growth under heat stress, in order to provided possible improvement hints for the development of heat-tolerant plants, especially food crops. Considering the impact of high temperature on agricultural production, we particularly focused on rice, an important food crop and model plant, reviewed the latest research progress in improving rice heat tolerance, and provided a review of multiple physiological and biochemical pathways that affect rice heat tolerance, including heat tolerance genes, transcription factors, and regulatory proteins. Finally, we introduced the current situation of breeding heat-tolerant rice and developing related germplasms, and how to use molecular means to assist the development of heat-tolerant rice in the near future.

How to improve the yield of crops has always been the focus of breeding research. Due to the population growth and global climate change, the demand for food has increased sharply, which has brought great challenges to agricultural production. In order to make up for the limitation of global cultivated land area, it is necessary to further improve the output of crops. Photosynthesis is the main source of plant assimilate accumulation, which has a profound impact on the formation of its yield. This review focuses on the cultivation of high light efficiency plants, introduces the main technical means and research progress in improving the photosynthetic efficiency of plants, and discusses the main problems and difficulties faced by the cultivation of high light efficiency plants. At the same time, in view of the frequent occurrence of high-temperature disasters caused by global warming, which seriously threatened plant normal production, we reviewed the response mechanism of plants to heat stress, introduced the methods and strategies of how to cultivate heat tolerant crops, especially rice, and briefly reviewed the progress of heat tolerant research at present. Given big progress in these area, the era of cultivating smart rice with high light efficiency and heat tolerance has come of age.

Wheat is a major food crop worldwide. The plant architecture is a complex trait mostly influenced by plant height, tiller number, and leaf morphology. Plant height plays a crucial role in lodging and thus affects yield and grain quality. In this study, a wheat population was genotyped by using Illumina iSelect 90K single nucleotide polymorphism (SNP) assay and finally 22,905 high-quality SNPs were used to perform a genome-wide association study (GWAS) for plant architectural traits employing four multi-locus GWAS (ML-GWAS) and three single-locus GWAS (SL-GWAS) models. As a result, 174 and 97 significant SNPs controlling plant architectural traits were detected by ML-GWAS and SL-GWAS methods, respectively. Among these SNP makers, 43 SNPs were consistently detected, including seven across multiple environments and 36 across multiple methods. Interestingly, five SNPs (Kukri_c34553_89, RAC875_c8121_1490, wsnp_Ex_rep_c66315_64480362, Ku_c5191_340, and tplb0049a09_1302) consistently detected across multiple environments and methods, played a role in modulating both plant height and flag leaf length. Furthermore, candidate SNPs (BS00068592_51, Kukri_c4750_452 and BS00022127_51) constantly repeated in different years and methods associated with flag leaf width and number of tillers. We also detected several SNPs (Jagger_c6772_80, RAC875_c8121_1490, BS00089954_51, Excalibur_01167_1207, and Ku_c5191_340) having common associations with more than one trait across multiple environments. By further appraising these GWAS methods, the pLARmEB and FarmCPU models outperformed in SNP detection compared to the other ML-GWAS and SL-GWAS methods, respectively. Totally, 152 candidate genes were found to be likely involved in plant growth and development. These finding will be helpful for better understanding of the genetic mechanism of architectural traits in wheat.

As the progenitor of durum wheat (Triticum durum Desf.) and common wheat (T. aestivum L.), wild emmer wheat (T. turgidum L. subsp. dicoccoides, TTD) has many valuable alleles for enlarging the genetic pool of common wheat. Chromosome arm substitution lines (CASLs) are useful genetic resources producing genome-wide variations in the background of certain cultivars, with each CASL containing a pair of an individual chromosome arms from the donor parent. Therefore, CASLs can be used to identify a broad range of phenotypes that are usually different from the parental lines, to map causal genes or quantitative trait loci and to broaden the genetic pools of existing cultivars as prebreeding materials. In this review we summarize recent progress in wheat genetic studies and breeding using two sets of CASLs of the wild emmer accession TTD140 in two common wheat backgrounds of 'Chinese Spring' and 'Bethlehem'. We report the production of CASLs, confirmation of their chromosome structure using molecular markers, and their application in discovering and mapping agronomically important genes. We propose that, together with the release of high-quality reference genomes of wild emmer and common wheat, wild emmer CASLs are useful resources for genetic study and breeding of wheat.

小麦是重要的粮食作物,春化作用能够促使小麦加速开花,是小麦发育过程中的一个重要质变过程.春化作用在一定遗传背景下,由多基因控制且受多种因素(如温度、光照等)影响.近年来,人们对小麦的春化作用进行了大量的研究,对小麦春化作用的调控机制及作用方式有了一定的认识,小麦的春化作用主要由Vrn-1、Vrn-2、Vrn-3和Vrn-4等4类主效基因调控,它们彼此作用,共同影响着小麦的冬春性.基于前人的研究,本文从小麦春化理论、春化条件及春化特性、春化过程中的生理变化和春化基因等4个方面对小麦的春化作用进行概述;此外,总结了小麦春化研究中存在的一些问题,并结合笔者自身试验提出了一些研究思路.

Heading date (HD) is an important agronomic trait, influencing directly or indirectly yield and quality traits. Previous experiments showed that the chromosome arm substitution line (CASL) 4AL of wild emmer in the background of Chinese Spring (CS) was about 18–22 days later in HD than CS. In this study, CASL4AL flowered roughly 20 days earlier than CS grown under long day (LD) with short day (SD) vernalization, but failed to flower when planted under controlled SD conditions. The above results suggest CASL4AL carries an extremely sensitive photoperiod response gene. CASL4AL showed a major difference from CS in restricted young spike development, remaining at the double-ridge stage and floret-primordium differentiation stage much longer than CS under SD. To map this gene, the F2 population from cross between CS and CASL4AL were explored in two consecutive years. In 2016, a HD related QTL flanked by M576 and wmc468 with a LOD score (8.5) was detected. In 2017, this QTL was repeatedly detected with a higher LOD score (10.03), and therefore named as QPpd.zafu-4A. A total of 27 genes were annotated and possible candidate was discussed. This work lays a foundation for map-based cloning of QPpd.zafu-4A and elucidating its molecular mechanism in affecting HD.

As the most important major food crop, rice (Oryza sativa) often suffers from heat stress in tropical and subtropical regions. Thus, to investigate the mechanisms of responses and tolerance to heat stress (HS) at the miRNA level is important for breeding new rice varieties with HS tolerance. In this study, six miRNA libraries (with duplicates for each of the 0 h, 12 h and 24 h HS treatment) for HT54, an indica heat tolerant line, were sequenced. Based on this, a set of HS-responsive miRNAs and their target genes were identified by using the next-generation sequencing (NGS) and degradome sequencing (DS). A total of 419 conserved and 77 novel miRNAs were identified, of which 39 conserved and 2 novel miRNAs were found to be significantly differentially expressed (p < 0.05). As the most up-regulated miRNA, the expression of miR396 family members were verified by qRT-PCR. In addition, one down-regulated miR162b and one novel miRNA (pc-5p-93188_29) were experimentally validated. These results inferred that these loci were responsive to HS. Moreover, a total of 1364 target transcripts were identified for 114 conserved miRNAs and a total of 65 were identified for 22 novel miRNA families. GO and pathway enrichment analyses showed that these genes most likely play vital roles in rice HS tolerance. Taken together, a set of HS-responsive conserved and novel miRNAs were firstly characterized and identified in rice seedlings, which would lay a solid foundation for clarifying rice HS response and tolerance mechanisms.

As one of the most vital major food crops feeding almost half the earth's population, rice often suffers from heat stress in tropical and subtropical regions. To study rice heat stress tolerance mechanism is critical for breeding new heat tolerant rice varieties. We performed RNA-Seq analysis to check rice transcriptomic differences responsive to heat stress in both heat-tolerant (HT, HT54) and heat-sensitive (HS, HT13) lines. A sum of 0.603 billion reads were acquired on behalf of 32,391 unique genes. Compared with 0 h, a sum of 2275 genes showed enhanced regulation while 2270 genes showed inhibited regulation in the HS line at 12 h, contrarily 2603 genes showed enhanced regulation and 2900 genes showed inhibited regulation in the HT line. A sum of 1438 genes showed enhanced regulation and 1237 genes showed inhibited regulation in the HS line at 24 h, contrarily 1599 genes showed enhanced regulation and 1754 genes showed inhibited regulation in the HT line. About 22,490 genes were assigned to gene ontology (GO) term in terms of biological process, cellular component and molecular function categories. Compared with 0 h, a sum of 8 and 4 genes showed different expression (RFC ≥ 2.0) between the HT and HS rice lines at 12 and 24 h, respectively. This work most probably set a solid foundation for elucidating the heat stress tolerance mechanisms and crop genetic improvement in rice.

Nonrandom segregation ratios of alleles 'segregation distortion' can have a striking impact on transmission genetics, and with widespread availability of genetic markers has been shown to be a frequent phenomenon. To investigate the possible effect of genetic interaction on segregation distortion and genetic map construction, the segregation and mapping of genetic markers locatedon wheat chromosomes 1A and 1B were followed in four recombinant substitution line (RSL) populations, produced using four chromosome-arm substitution lines (CASLs 1AS, 1AL, 1BS and 1BL) of wild emmer (Triticum turgidum var. dicoccoides, accession TTD140) in the background of the common wheat (T. aestivum) cultivar Bethlehem (BLH), each crossed to BLH itself. Using these four RSL populations, four genetic maps of chromosome 1 arms were constructed. A total of 22 genetic markers representing 19 loci were assigned to chromosome 1A, and 32 markers representing 30 loci were assigned to 1B. For chromosome 1B, two linkage maps were also constructed using RFLP data of an F2 population derived from the same cross combination as the RSLs. The RSL and F2 maps varied in genetic distances, but showed the same linear order of DNA markers. Segregation analysis revealed strong selection against BLH alleles on chromosome 1B, skewing the allelic frequency distribution in favour of TTD in both F2 and RSL populations at all marker loci. On the contrary, strong selection against TTD alleles on chromosome 1A was detected for some loci in the BLH × CASL1AL RSLs, and their distribution was significantly skewed to BLH. F2 populations always showed more segregation distortion than the corresponding RSLs. More markers near the region of chromosome 1B shared by both CASL1BS and 1BL (∼55 cM on chromosome 1B across the centromere) showed significantly distorted segregation in the BLH × CASL1BL population than in thecorresponding BLH × CASL1BS populations. Six markers located on chromosome 1A region shared by CASL1AS and 1AL showed significantly distorted segregation in 1AL-RSL, while no marker showed distorted segregation in 1AS-RSL. These results indicated that genetic factor(s) in the centromere region cause the distorted segregation of genetic markers on wheat chromosome 1B.

MiRNA is a non-coding small RNA in eukaryotic organisms.It plays an important role in the development of animals and plants.However,the molecular mechanism of rice resistance to high temperature participated by miRNA has seldom been studied.As an important staple food,rice (Oryza sativa) frequently suffers from heat stress during the growing season.Clarifying plant heat stress response and tolerance mechanism at miRNA level is the basis to breed varieties with a suitable heat stress (HS) tolerance.In previous study,six libraries (double for 0,12 and 24 h heat treatment) constructed from heat tolerant variety Oryza sativa ssp.indica cv.HT54,were sequenced by next-generation sequencing (NGS) technique.Those study found that the miR396 family member and their putative target genes might play pivotal roles as regulator reacting to heat stress.In this study,the expression of all 8 miR396 family members and 12 predicted target genes were detected in seedlings of Oryza sativa spp.japonica cv.Nipponbare with 48 ℃ heat stress for 6 different time points.The results indicated that all 8 miR396 family members and 12 predicted target genes showed different reaction to heat stress.The expression level of miR396a,miR396e and miR396f increased at high temperature stress at each time points,the expression level increased up to 10 fold (in miR396a and miR396e),even 100-fold (in miR396f);while miR396b,miR396c,miR396d,miR396g and miR396h decreased at 1.5,3,6 h,but increased at 12,24 h.Correspondingly,the OsGRF family showed irregular upward or descending expression with high temperature stress.The target gene OsGRF2 decreased up to 8～10-fold.OsGRF2 had a high negative correlation with the expression of miR396a,miR396e and miR396f,indicating that OsGRF2 was the target gene for miR396a,miR396e and miR396f.These results suggest that miR396 would play a key role in rice heat tolerance.