Crop Journal最新文献

Maize (Zea mays L.) is a global cereal crop whose demand is projected to double by 2050. Along with worsening of farmland salinization, salt stress has become a major environmental threat to the sustainability of maize production worldwide. Accordingly, there is an urgent need to decipher salt-tolerant mechanisms and facilitate the breeding of salt-tolerant maize. As salt tolerance is a complex trait regulated by multiple genes, and maize germplasm varies widely in salt tolerance, efforts have been devoted to the identification and application of quantitative-trait loci (QTL) for salt tolerance. QTL associated with ion regulation, osmotic tolerance, and other aspects of salt tolerance have been discovered using genome-wide association studies (GWAS), linkage mapping, and omics-based approaches. This review highlights recent advances in the molecular-level understanding of salt stress response in maize, in particular in (a) the discovery of salt-tolerance QTL, (b) the mechanisms of salt tolerance, (c) the development of salt-tolerant maize cultivars, and (d) current challenges and future prospects.

Chlorophyll, a green pigment in photosynthetic organisms, is generated by two distinct biochemical pathways, the tetrapyrrole biosynthetic pathway (TBP) and the methylerythritol 4-phosphate (MEP) pathway. MEP is one of the pathways for isoprenoid synthesis in plants, with 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR) catalyzing its last step. In this study, we isolated a green-revertible yellow leaf mutant gry3 in rice and cloned the GRY3 gene, which encodes a HDR participating in geranylgeranyl diphosphate (GGPP) biosynthesis in chloroplast. A complementation experiment confirmed that a missense mutation (C to T) in the fourth exon of LOC_Os03g52170 causes the gry3 phenotype. Under high temperature and high light, transcript and protein abundances of GRY3 were reduced in the gry3 mutant. Transcriptional expression of chlorophyll biosynthesis, chloroplast development, and genes involved in photosynthesis were also affected. Excessive reactive oxygen species accumulation, cell death, and photosynthetic proteins degradation were occurred in the mutant. The content of GGPP was reduced in gry3 compared with Nipponbare, resulting in a stoichiometric imbalance of tetrapyrrolic chlorophyll precursors. These results shed light on the response of chloroplast biogenesis and maintenance in plants to high-temperature and high-light stress.

Waterlogging is a growing threat to wheat production in high-rainfall areas. In this study, a doubled haploid (DH) population developed from a cross between Yangmai 16 (waterlogging-tolerant) and Zhongmai 895 (waterlogging-sensitive) was used to map quantitative trait loci (QTL) for waterlogging tolerance using a high-density 660K single-nucleotide polymorphism (SNP) array. Two experimental designs, waterlogging concrete tank (CT) and waterlogging plastic tank (PT), were used to simulate waterlogging during anthesis in five environments across three growing seasons. Waterlogging significantly decreased thousand-kernel weight (TKW) relative to non-waterlogged controls, although the degree varied across lines. Three QTL for waterlogging tolerance were identified on chromosomes 4AL, 5AS, and 7DL in at least two environments. All favorable alleles were contributed by the waterlogging-tolerant parent Yangmai 16. QWTC.caas-4AL exhibited pleiotropic effects on both enhancing waterlogging tolerance and decreasing plant height. Six high-confidence genes were annotated within the QTL interval. The combined effects of QWTC.caas-4AL and QWTC.caas-5AS greatly improved waterlogging tolerance, while the combined effects of all three identified QTL (QWTC.caas-4AL, QWTC.caas-5AS, and QWTC.caas-7DL) exhibited the most significant effect on waterlogging tolerance. Breeder-friendly kompetitive allele-specific PCR (KASP) markers (K_AX_111523809, K_AX_108971224, and K_AX_110553316) flanking the interval of QWTC.caas-4AL, QWTC.caas-5AS, and QWTC.caas-7DL were produced. These markers were tested in a collection of 240 wheat accessions, and three superior polymorphisms of the markers distributed over 67 elite cultivars in the test population, from the Chinese provinces of Jiangsu, Anhui, and Hubei. The three KASP markers could be used for marker-assisted selection (MAS) to improve waterlogging tolerance in wheat.

Root architecture development, an agronomic trait that influences crop yield, is regulated by multiple plant hormones. Abscisic acid (ABA) is a stress hormone that responds to multiple stresses, including salt, drought, and cold stress, and modulates various aspects of plant growth and development. In recent years, it has been found that ABA synthesized under mild stress or well-watered conditions can support plant growth and stress resistance by positively regulating root architecture development. In this review, we summarize the molecular, cellular, and organismal basis of ABA homeostasis in the root and how ABA signaling affects root architecture development both as an inhibitor and as an activator. We discuss the implications of these studies and the potential for exploiting the components of ABA signaling in designing crop plants with improved root system development and stress resistance.

During seed germination, the cotton chaperone protein HSP24.7 regulates the release, from the mitochondrial electron transport chain, of reactive oxygen species (ROS), a stimulative signal regulating germination. The function of HSP24.7 during vegetative stages remains largely unknown. Here we propose that suppression of GhHSP24.7 in cotton seedlings increases tolerance to heat and drought stress. Elevation of GhHSP24.7 was found to be positively associated with endogenous levels of ROS. We identified a new client protein of GhHSP24.7, cotton lysine deacetylase (GhHDA14), which is involved in mitochondrial protein modification. Elevated levels of GhHSP24.7 suppressed deacetylase activity in mitochondria, leading to increased acetylation of mitochondrial proteins enriched in the subunit of F-type ATPase, V-type ATPase, and cytochrome C reductase, ultimately reducing leaf ATP content. Consequently, in combination with altered ROS content, GhHSP24.7 transgenic lines were unable to coordinate stomatal closure under stress. The regulation circuit composed of GhHSP24.7 and GhHDA14 represents a post-translation level mechanism in plant abiotic stress responses that integrates the regulation of ROS and ATP.

Chilling-induced accumulation of reactive oxygen species (ROS) is harmful to plants, which usually produce anthocyanins to scavenge ROS as protection from chilling stress. As a tropical crop, cassava is hypersensitive to chilling, but the biochemical basis of this hypersensitivity remains unclear. We previously generated MeMYB2-RNAi transgenic cassava with increased chilling tolerance. Here we report that MeMYB2-RNAi transgenic cassava accumulated less ROS but more cyanidin-3-O-glucoside than the wild type under early chilling stress. Under this stress, the anthocyanin biosynthesis pathway was more active in MeMYB2-RNAi lines than in the wild type, and several genes involved in the pathway, including MeTT8, were up-regulated by MeMYB2-RNAi in the transgenic cassava. MeMYB2 bound to the MeTT8 promoter and blocked its expression under both normal and chilling conditions, thereby inhibiting anthocyanin accumulation. MeTT8 was shown to bind to the promoter of Dihydroflavonol 4-reductase (MeDFR-2) and increased MeDFR-2 expression. MeMYB2 appears to act as an inhibitor of chilling-induced anthocyanin accumulation during the rapid response of cassava to chilling stress.

Acid soils occupy approximately 50% of potentially arable lands. Improving crop productivity in acid soils, therefore, will be crucial for ensuring food security and agricultural sustainability. High soil acidity often coexists with phosphorus (P) deficiency and aluminum (Al) toxicity, a combination that severely impedes crop growth and yield across wide areas. As roots explore soil for the nutrients and water required for plant growth and development, they also sense and respond to below-ground stresses. Within the terrestrial context of widespread P deficiency and Al toxicity pressures, plants, particularly roots, have evolved a variety of mechanisms for adapting to these stresses. As legumes, soybean (Glycine max) plants may acquire nitrogen (N) through symbiotic nitrogen fixation (SNF), an adaptation that can be useful for mitigating excessive N fertilizer use, either directly as leguminous crop participants in rotation and intercropping systems, or secondarily as green manure cover crops. In this review, we investigate legumes, especially soybean, for recent advances in our understanding of root-based mechanisms linked with root architecture modification, exudation and symbiosis, together with associated genetic and molecular strategies in adaptation to individual and/or interacting P and Al conditions in acid soils. We propose that breeding legume cultivars with superior nutrient efficiency and/or Al tolerance traits through genetic selection might become a potentially powerful strategy for producing crop varieties capable of maintaining or improving yields in more stressful soil conditions subjected to increasingly challenging environmental conditions.

Drought-induced protein 19 (Di19) is a Cys2/His2 zinc-finger protein that functions in plant growth and development and in tolerance to abiotic stresses. GmPUB21, an E3 ubiquitin ligase, negatively regulates drought and salinity response in soybean. We identified potential interaction target proteins of GmPUB21 by yeast two-hybrid cDNA library screening, GmDi19-5 as a candidate. Bimolecular fluorescence complementation and glutathionine-S-transferase pull-down assays confirmed the interaction between GmDi19-5 and GmPUB21. GmDi19-5 was induced by NaCl, drought, and abscisic acid (ABA) treatments. GmDi19-5 was expressed in the cytoplasm and nucleus. GmDi19-5 overexpression conferred hypersensitivity to drought and high salinity, whereas GmDi19-5 silencing increased drought and salinity tolerance. Transcripts of ABA- and stress response-associated genes including GmRAB18 and GmDREB2A were down-regulated in GmDi19-5-overexpressing plants under drought and salinity stresses. ABA decreased the protein level of GmDi19-5 in vivo, whereas GmPUB21 increased the decrease of GmDi19-5 after exogenous ABA application. The accumulation of GmPUB21 was also inhibited by GmDi19-5. We conclude that GmPUB21 and GmDi19-5 collaborate to regulate drought and salinity tolerance via an ABA-dependent pathway.

Climate change-induced heat stress combines two challenges: high day- and nighttime temperatures, and physiological water deficit due to demand-side drought caused by increase in vapor-pressure deficit. It is one of the major factors in low productivity of maize in rainfed stress-prone environments in South Asia, affecting a large population of smallholder farmers who depend on maize for their sustenance and livelihoods. The International Maize and Wheat Improvement Center (CIMMYT) maize program in Asia, in partnership with public-sector maize research institutes and private-sector seed companies in South Asian countries, is implementing an intensive initiative for developing and deploying heat-tolerant maize that combines high yield potential with resilience to heat and drought stresses. With the integration of novel breeding tools and methods, including genomics-assisted breeding, doubled haploidy, field-based precision phenotyping, and trait-based selection, new maize germplasm with increased tolerance to heat stress is being developed for the South Asian tropics. Over a decade of concerted effort has resulted in the successful development and release of 20 high-yielding heat-tolerant maize hybrids in CIMMYT genetic backgrounds. Via public–private partnerships, eight hybrids are presently being deployed on over 50,000 ha in South Asian countries, including Bangladesh, Bhutan, India, Nepal, and Pakistan.

Although the use of heterosis in maize breeding has increased crop productivity, the genetic causes underlying heterosis for nitrogen (N) use efficiency (NUE) have been insufficiently investigated. In this study, five N-response traits and five low-N-tolerance traits were investigated using two inbred line populations (ILs) consisting of recombinant inbred lines (RIL) and advanced backcross (ABL) populations, derived from crossing Ye478 with Wu312. Both populations were crossed with P178 to construct two testcross populations. IL populations, their testcross populations, and the midparent heterosis (MPH) for NUE were investigated. Kernel weight, kernel number, and kernel number per row were sensitive to N level and ILs showed higher N response than did the testcross populations. Based on a high-density linkage map, 138 quantitative trait loci (QTL) were mapped, each explaining 5.6%–38.8% of genetic variation. There were 52, 34 and 52 QTL for IL populations, MPH, and testcross populations, respectively. The finding that 7.6% of QTL were common to the ILs and their testcross populations and that 11.7% were common to the MPH and testcross population indicated that heterosis for NUE traits was regulated by non-additive and non-dominant loci. A QTL on chromosome 5 explained 27% of genetic variation in all of the traits and Gln1-3 was identified as a candidate gene for this QTL. Genome-wide prediction of NUE traits in the testcross populations showed 14%–51% accuracy. Our results may be useful for clarifying the genetic basis of heterosis for NUE traits and the candidate gene may be used for genetic improvement of maize NUE.