Pollen Abortion Research Articles

Disruption of Energy Metabolism and Reactive Oxygen Species Homeostasis in Honglian Type-Cytoplasmic Male Sterility (HL-CMS) Rice Pollen

Honglian type-cytoplasmic male sterility (HL-CMS) is caused by the inter-communication between the nucleus and mitochondria. However, the mechanisms by which sterility genes regulate metabolic alterations and changes in mitochondrial morphology in the pollen of HL-CMS remains unclear. In this study, we compared the morphological differences between the pollen of the male sterile line YA and the near-isogenic line NIL-Rf6 using hematoxylin and eosin staining as well as 4ʹ,6-diamidino- 2-phenylindole (DAPI) staining. HL-CMS is characterized by gametophytic sterility, where the aborted pollen grains are empty and the tapetal layer remains intact. Transmission electron microscopy was employed to observe mitochondrial morphological changes at the microspore stage, revealing that significant mitochondrial alternations, characterized by the formation of 'large spherical mitochondria', occurred at the binucleate stage in the YA line. Additionally, metabolomics analysis revealed decreased levels of metabolites associated with the carbohydrate and flavonoid pathways. Notably, the decrease in flavonoids was found to contribute to an elevation in reactive oxygen species (ROS) levels. Therefore, we propose a model in which rice fertility is modulated by the levels of pollen carbohydrates and flavonoid metabolites, with impaired mitochondrial energy production and reduced flavonoid biosynthesis being the main causes of ROS accumulation and pollen abortion in rice.

Integrated cytological, physiological, and comparative transcriptome profiling reveals the regulatory network for male sterility in Welsh onion (Allium fistulosum L.)

Welsh onion (Allium fistulosum L.) is a specialty crop with value as a vegetable, condiment, and medicine. However, the molecular mechanisms related to pollen abortion and cytoplasmic male sterility are poorly understood, limiting the heterosis utilization and hybrid production of A. fistulosum. This study investigated the dynamic differences between male-sterile (MS) plants and male-fertile (MF) plants at different anther developmental stages based on integrated cytological, physiological, and transcriptomic analyses. Cytological observations revealed that pollen abortion in the MS plants began during the tetrad stage and was caused by vacuolated microspores, abnormal degradation of the tapetum, and inadequate nutrient supply. The physiological results showed that MS plants exhibited low total soluble sugar and starch contents and decreased antioxidant enzyme activities (peroxidase and catalase). Comparative transcriptome analysis identified 7005 differentially expressed genes (DEGs) and functional enrichment analysis indicated that significant transcriptomic differences were related to oxidative phosphorylation, starch and sucrose metabolism, and cutin, suberine, and wax biosynthesis. The relative expression levels of key DEGs in these three important metabolic pathways were determined using quantitative real-time polymerase chain reaction. On this basis, a core transcriptome-mediated MS network was proposed for MS plants with four functional components: inhibited sucrose synthesis and transport; blocked cutin, suberine, and wax synthesis; accelerated reactive oxygen species generation; and abnormal tapetal programmed cell death. These results provide theoretical guidance for further exploring the molecular mechanisms of male sterility in A. fistulosum.

OsSNDP4, a Sec14-nodulin Domain Protein, is Required for Pollen Development in Rice

Pollen is encased in a robust wall that shields the male gametophyte from various stresses and aids in pollination. The pollen wall consists of gametophyte-derived intine and sporophyte-derived exine. The exine is mainly composed of sporopollenin, which is biopolymers of aliphatic lipids and phenolics. The process of exine formation has been the subject of extensive research, yet the underlying molecular mechanisms remain elusive. In this study, we identified a rice mutant of the OsSNDP4 gene that is impaired in pollen development. We demonstrated that OsSNDP4, a putative Sec14-nodulin domain protein, exhibits a preference for binding to phosphatidylinositol (3)-phosphate [PI(3)P], a lipid primarily found in endosomal and vacuolar membranes. The OsSNDP4 protein was detected in association with the endoplasmic reticulum (ER), vacuolar membranes, and the nucleus. OsSNDP4 expression was detected in all tested organs but was notably higher in anthers during exine development. Loss of OsSNDP4 function led to abnormal vacuole dynamics, inhibition in Ubisch body development, and premature degradation of cellular contents and organelles in the tapetal cells. Microspores from the ossndp4 mutant plant displayed abnormal exine formation, abnormal vacuole enlargement, and ultimately, pollen abortion. RNA-seq assay revealed that genes involved in the biosynthesis of fatty acid and secondary metabolites, the biosynthesis of lipid polymers, and exosome formation were enriched among the down-regulated genes in the mutant anthers, which correlated with the morphological defects observed in the mutant anthers. Base on these findings, we propose that OsSNDP4 regulates pollen development by binding to PI(3)P and influencing the dynamics of membrane systems. The involvement of membrane systems in the regulation of sporopollenin biosynthesis, Ubisch body formation, and exine formation provides a novel mechanism regulating pollen wall development.

In-Depth Understanding of Cytoplasmic Male Sterility by Metabolomics in Spring Stem Mustard (Brassica juncea var. tumida Tsen et Lee)

Male sterility (MS) caused by aborted pollen is a vital germplasm resource. In this study, metabolomic, transcriptomic, and proteomic analyses were performed to investigate the molecular regulatory mechanism of cytoplasmic male sterility (CMS) in the flower buds of the male sterile line 09-05A and its maintainer line, 09-05B, of Brassica juncea. Our metabolomic analysis revealed that 41 metabolites involved in pollen development and male fertility formation were differentially accumulated between 09-05A and 09-05B at the bi-nucleate stage of B. juncea. Integrated omics indicated that the expression of key genes and proteins in the amino acid and phenylpropanoid metabolic pathways was remarkably downregulated in the flower buds of 09-05A. Furthermore, the abnormal expression of key transcription factor (TF) genes related to tapetum development and pollen wall formation may affect pollen development in the 09-05A CMS line. The results indicated that the downregulated expression level of critical genes and proteins in amino acid metabolism; phenylpropanoid synthesis; and TF genes, such as shikimate kinase, phenylalanine ammonia-lyase, and MYB103, may have led to impaired tapetum and pollen wall development, thereby causing pollen abortion in 09-05A. This study provides new insights into the metabolic and molecular regulatory mechanisms underlying the formation of CMS in B. juncea and lays a foundation for detailed studies on the identity and characteristics of MS-related genes.

Morphological and cytological assessments reveal pollen degradation causes pollen abortion in cotton cytoplasmic male sterility lines

BackgroundUnderstanding the mechanism of male sterility is crucial for producing hybrid seeds and developing sterile germplasm resources. However, only a few cytoplasmic male sterility (CMS) lines of cotton have been produced due to several challenges, like inadequate variation of agronomic traits, incomplete sterility, weak resilience of restorer lines, and difficulty in combining strong dominance. Therefore, the morphological and cytological identification of CMS in cotton will facilitate hybrid breeding.ResultsTwo F2 segregating populations of cotton were constructed from cytoplasmic male sterile lines (HaA and 01A, maternal) and restorer lines (HaR and 26R, paternal). Genetic analysis of these populations revealed a segregation ratio of 3:1 for fertile to sterile plants. Phenotypic analysis indicated no significant differences in traits of flower bud development between sterile and fertile plants. However, sterile plants exhibited smaller floral organs, shortened filament lengths, and anther atrophy on the flowering day in comparison with the fertile plants. When performed scanning electron microscopy (SEM), the two F2 populations revealed morphological variations in the anther epidermis. Cellular analysis showed no significant differences in pollen development before pollen maturation. Interestingly, between the pollen maturation and flowering stages, the tapetum layer of sterile plants degenerated prematurely, resulting in abnormal pollen grains and gradual pollen degradation.ConclusionThe results of this study suggest that fertility-restoring genes are controlled by a single dominant gene. Sterile plants exhibit distinctive floral morphology, which is characterized by stamen atrophy and abnormal anthers. Pollen abortion occurs between pollen maturity and flowering, indicating that premature tapetum degradation may be the primary cause of pollen abortion. Overall, our study provides a theoretical basis for utilizing CMS in hybrid breeding and in-depth investigation of the dominant configuration of cotton hybrid combinations, mechanisms of sterility, and the role of sterile and restorer genes.

The characteristic analysis of TaTDF1 reveals its function related to male sterility in wheat (Triticum aestivum L.)

BackgroundThe male sterile lines are an important foundation for heterosis utilization in wheat (Triticum aestivum L.). Thereinto, pollen development is one of the indispensable processes of wheat reproductive development, and its fertility plays an important role in wheat heterosis utilization, and are usually influencing by genes. However, these key genes and their regulatory networks during pollen abortion are poorly understood in wheat.ResultsDEFECTIVE IN TAPETAL DEVELOPMENT AND FUNCTION 1 (TDF1) is a member of the R2R3-MYB family and has been shown to be essential for early tapetal layer development and pollen grain fertility in rice (Oryza sativa L.) and Arabidopsis thaliana. In order to clarify the function of TDF1 in wheat anthers development, we used OsTDF1 gene as a reference sequence and homologous cloned wheat TaTDF1 gene. TaTDF1 is localized in the nucleus. The average bolting time of Arabidopsis thaliana overexpressed strain (TaTDF1-OE) was 33 d, and its anther could be colored normally by Alexander staining solution, showing red. The dominant Mosaic suppression silence-line (TaTDF1-EAR) was blue-green in color, and the anthers were shrimpy and thin. The TaTDF1 interacting protein (TaMAP65) was confirmed using Yeast Two-Hybrid Assay (Y2H) and Bimolecular-Fluorescence Complementation (BiFC) experiments. The results showed that downregulated expression of TaTDF1 and TaMAP65 could cause anthers to be smaller and shrunken, leading to pollen abortion in TaTDF1 wheat plants induced by virus-induced gene-silencing technology. The expression pattern of TaTDF1 was influenced by TaMAP65.ConclusionsThus, systematically revealing the regulatory mechanism of wheat TaTDF1 during anther and pollen grain development may provide new information on the molecular mechanism of pollen abortion in wheat.

Identification of anther thermotolerance genes by the integration of linkage and association analysis in maize.

Maize is one of the world's most important staple crops, yet its production is increasingly threatened by the rising frequency of high-temperature stress (HTS). To investigate the genetic basis of anther thermotolerance under field conditions, we performed linkage and association analysis to identify HTS response quantitative trait loci (QTL) using three recombinant inbred line (RIL) populations and an association panel containing 375 diverse maize inbred lines. These analyses resulted in the identification of 16 co-located large QTL intervals. Among the 37 candidate genes identified in these QTL intervals, five have rice or Arabidopsis homologs known to influence pollen and filament development. Notably, one of the candidate genes, ZmDUP707, has been subject to selection pressure during breeding. Its expression is suppressed by HTS, leading to pollen abortion and barren seeds. We also identified several additional candidate genes potentially underly QTL previously reported by other researchers. Taken together, our results provide a pool of valuable candidate genes that could be employed by future breeding programs aiming at enhancing maize HTS tolerance.

Abnormal Degraded Tapetum1 (ADT1) is required for tapetal cell death and pollen development in rice.

The timely degradation of tapetum, the innermost somatic anther cell layer in flowering plants, is critical for pollen development. Although several genes involved in tapetum development have been characterized, the molecular mechanisms underlying tapetum degeneration remain elusive. Here, we showed that mutation in Abnormal Degraded Tapetum1 (ADT1)resulted in overaccumulation of Reactive Oxygen Species (ROS) and abnormal anther development, causing earlier tapetum Programmed Cell Death (PCD) and pollen abortion. ADT1 encodes a nuclear membrane localized protein, which is strongly expressed in the developing microspores and tapetal cells during early anther development. Moreover, ADT1 could interact with metallothionein MT2b, which was related to ROS scavenging and cell death regulation. These findings indicate that ADT1 is required for proper timing of tapetum PCD by regulating ROS homeostasis, expanding our understanding of the regulatory network of male reproductive development in rice.

Arabidopsis Sar1b is critical for pollen tube growth.

Pollen tube growth is an essential step leading to reproductive success in flowering plants, in which vesicular trafficking plays a key role. Vesicular trafficking from endoplasmic reticulum to the Golgi apparatus is mediated by the coat protein complex II (COPII). A key component of COPII is small GTPase Sar1. Five Sar1 isoforms are encoded in the Arabidopsis genome and they show distinct while redundant roles in various cellular and developmental processes, especially in reproduction. Arabidopsis Sar1b is essential for sporophytic control of pollen development while Sar1b and Sar1c are critical for gametophytic control of pollen development. Because functional loss of Sar1b and Sar1c resulted in pollen abortion, whether they influence pollen tube growth was unclear. Here we demonstrate that Sar1b mediates pollen tube growth, in addition to its role in pollen development. Although functional loss of Sar1b does not affect pollen germination, it causes a significant reduction in male transmission and of pollen tube penetration of style. We further show that membrane dynamics at the apex of pollen tubes are compromised by Sar1b loss-of-function. Results presented provide further support of functional complexity of the Sar1 isoforms.

Regulatory Mechanisms of Pollen Development: Transcriptomic and Bioinformatic Insights into the Role of β-1,3 Glucanase Gene (LbGlu1) in Lycium barbarum

Pollen fertility is a critical factor in seed development and crop breeding. Extensive studies have explored the mechanisms of pollen fertility in model plants and economic crops. However, the mechanisms of pollen abortion in medicinal and edible plants, including Lycium barbarum, remain elusive. This study utilized transcriptome analysis to identify key genes and regulatory networks implicated in pollen fertility in L. barbarum. The results demonstrated differential expression of 12,185 genes (DEGs) between the sterile and fertile lines, encompassing 489 genes that exhibited variation across the five stages of pollen development. Additionally, GO and KEGG enrichment analyses indicated that the DEGs were predominantly associated with energy metabolism, carbohydrate metabolism, and notably, hydrolase activity. Co-expression network analysis unveiled two modules intimately associated with fertility, each comprising 908 and 756 hub genes, incorporating β-1,3-glucanase genes (Glu) and co-expressed transcription factors (TFs). Phylogenetic analysis implied that LbGlu1 was a potential candidate gene implicated in regulating pollen abortion in L. barbarum. This work advances a novel understanding of pollen abortion in L. barbarum and offers theoretical support for the utilization of sterility genes to enhance crop improvement.

The mitochondrial orf117Sha gene desynchronizes pollen development and causes pollen abortion in Arabidopsis Sha cytoplasmic male sterility.

Cytoplasmic male sterility (CMS) is of major agronomical relevance in hybrid breeding. In gametophytic CMS, abortion of pollen is determined by the grain genotype, while in sporophytic CMS, it is determined by the mother plant genotype. While several CMS mechanisms have been dissected at the molecular level, gametophytic CMS has not been straightforwardly accessible. We used the gametophytic Sha-CMS in Arabidopsis to characterize the cause and process of pollen abortion by implementing in vivo biosensing in single pollen and mitoTALEN mutagenesis. We obtained conclusive evidence that orf117Sha is the CMS-causing gene, despite distinct characteristics from other CMS genes. We measured the in vivo cytosolic ATP content in single pollen, followed pollen development, and analyzed pollen mitochondrial volume in two genotypes that differed only by the presence of the orf117Sha locus. Our results showed that the Sha-CMS is not triggered by ATP deficiency. Instead, we observed desynchronization of a pollen developmental program. Pollen death occurred independently in pollen grains at diverse stages and was preceded by mitochondrial swelling. We conclude that pollen death is grain-autonomous in Sha-CMS and propose that mitochondrial permeability transition, which was previously described as a hallmark of developmental and environmental-triggered cell death programs, precedes pollen death in Sha-CMS.

‘Juxiangyuan’ Seedless Orange: A New Mutant with Male and Female Sterility

Seedless is a highly valued commercial characteristic in the citrus industry, both for fresh consumption and for processed markets. In this study, the ‘Succari Sweet Orange’ (WT) and its seedless mutant ‘Juxiangyuan’ (MT), which originated from a bud mutation, were selected to study the formation of a citrus seedless phenotype. Microscopic analysis of MT’s floral organs, including anther and ovary cross-sections, provides insights into its seedless phenotype compared to the original seeded cultivar. Additionally, pollen features, viability, and in vitro germination were examined to determine the cause of seedlessness. MT exhibited significant developmental deformities in both male and female gametes, with pollen grain analysis indicating a high rate of deformity (41.48%), low viability (9.59%), and minimal in vitro germination (9.56%). Hybridization experiments were conducted to assess male and female sterility and pollen incompatibility. Both WT and MT exhibited parthenocarpic development. Notably, MT fruit produced with an average of 3.51 seeds pollinated to WT, despite severe pollen abortion of MT. MT, however, produced seedless fruit through self-breeding or cross-breeding with other varieties, demonstrating stable female sterility. Despite reduced pollen quantity and viability in the seedless mutant ‘Juxiangyuan’, its seedlessness primarily stems from female sterility. This study contributed to a deeper understanding of seedless formation in ‘Juxiangyuan’ and provided valuable information relevant to its commercial cultivation.

Regulation of carbohydrate metabolism during anther development in a thermo-sensitive genic male-sterile wheat line.

Bainong sterility (BNS) is a thermo-sensitive genic male sterile wheat line, characterised by anther fertility transformation in response to low temperature (LT) stress during meiosis, the failure of vacuole decomposition and the absence of starch accumulation in sterile bicellular pollen. Our study demonstrates that the late microspore (LM) stage marks the transition from the anther growth to anther maturation phase, characterised by the changes in anther structure, carbohydrate metabolism and the main transport pathway of sucrose (Suc). Fructan is a main storage polysaccharide in wheat anther, and its synthesis and remobilisation are crucial for anther development. Moreover, the process of pollen amylogenesis and the fate of the large vacuole in pollen are closely intertwined with fructan synthesis and remobilisation. LT disrupts the normal physiological metabolism of BNS anthers during meiosis, particularly affecting carbohydrate metabolism, thus determining the fate of male gametophytes and pollen abortion. Disruption of fructan synthesis and remobilisation regulation serves as a decisive event that results in anther abortion. Sterile pollen exhibits common traits of pollen starvation and impaired starch accumulation due to the inhibition of apoplastic transport starting from the LM stage, which is regulated by cell wall invertase TaIVR1 and Suc transporter TaSUT1.

Abnormal Calcium Accumulation and ROS Homeostasis-Induced Tapetal Programmed Cell Death Lead to Pollen Abortion of Petaloid-Type Cytoplasmic Male Sterility in Camellia oleifera

Cytoplasmic male sterility (CMS) plays a crucial role in the utilization of heterosis. The petaloid anther abortion in oil tea (Camellia oleifera Abel.) constitutes a CMS phenomenon, which is of great value for the hybrid breeding of oil tea. However, as the mechanism of its CMS is still poorly understood, it is necessary to study the cytology and physiological characteristics of anther abortion. In this study, a C. oleifera cultivar, Huashuo (HS), and its petalized CMS mutant (HSP) were used as materials to explore this mechanism. Compared with HS, cytological analysis demonstrated that HSP showed early-onset tapetum programmed cell death (PCD) and an organelle disorder phenotype during the tetrad stage. In HSP, anthers exhibited elevated levels of calcium deposition in anther wall tissues, tapetum layers, and microspores, and yet calcium accumulation was abnormal at the later stage. The contents of hydrogen peroxide and MDA in HSP anthers were higher, and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were lower than those of HS, which resulted in an excessive accumulation of reactive oxygen species (ROS). Real-time quantitative PCR confirmed that the transcription levels of CoPOD and CoCAT genes encoding key antioxidant enzymes in HSP were downregulated compared with HS in early pollen development; the gene CoCPK, which encodes a calcium-dependent protein kinase associated with antioxidase, was upregulated during the critical period. Thus, we suggest that excessive ROS as a signal breaks the balance of the antioxidant system, and along with an abnormal distribution of calcium ions, leads to the early initiation of PCD in the tapetum, and ultimately leads to pollen abortion for HSP. These results lay a cytological and physiological foundation for further studies on the CMS mechanism, and provide information for breeding male-sterile lines of C. oleifera.

DIA-based proteome profiling with PRM verification reveals the involvement of ER-associated protein processing in pollen abortion in Ogura CMS cabbage

Ogura cytoplasmic male sterility (Ogura CMS) is extensively applied in hybrid seed production in cruciferous crops. However, the post-transcriptional molecular basis of Ogura CMS in cruciferous crops remains elusive. Here, a data-independent acquisition-based proteomic approach coupled with a parallel reaction monitoring-based targeted proteomic assay was used to analyze the proteome dynamics of Ogura CMS cabbage line RM and its maintainer line RF during floral bud development to obtain insights into the mechanism underlying Ogura CMS in cruciferous crops. A total of 9 162 proteins corresponding to 61 464 peptides were identified in RM and RF floral buds. The proteomic fluctuation of RM was weaker than that of RF. Differences in protein expression between RM and RF gradually enlarged with floral bud development. Fifteen continually up-regulated and eight continually down-regulated proteins were found in RM relative to RF throughout floral bud development. Differentially expressed proteins between RM and RF during floral bud development were implicated in the endoplasmic reticulum (ER)-associated protein processing pathway, in which most of them exhibited down-regulated expression in RM. These data suggest that ER-associated protein processing may be involved in pollen abortion in Ogura CMS cabbage by inhibiting the expression of critical factors. Our findings not only deepen the understanding of the molecular mechanisms of Ogura CMS in cruciferous crops but also provide better guidance for applying Ogura CMS in the hybrid breeding of cruciferous crops.

The R2R3 MYB gene TaMYB305 positively regulates anther and pollen development in thermo-sensitive male-sterility wheat with Aegilops kotschyi cytoplasm.

The loss of TaMYB305 function down-regulated the expression of jasmonic acid synthesis pathway genes, which may disturb the jasmonic acid synthesis, resulting in abnormal pollen development and reduced fertility. The MYB family, as one of the largest transcription factor families found in plants, regulates plant development, especially the development of anthers. Therefore, it is important to identify potential MYB transcription factors associated with pollen development and to study its role in pollen development. Here, the transcripts of an R2R3 MYB gene TaMYB305 from KTM3315A, a thermo-sensitive cytoplasmic male-sterility line with Aegilops kotschyi cytoplasm (K-TCMS) wheat, was isolated. Quantitative real-time PCR (qRT-PCR) and promoter activity analysis revealed that TaMYB305 was primarily expressed in anthers. The TaMYB305 protein was localized in the nucleus, as determined by subcellular localization analysis. Our data demonstrated that silencing of TaMYB305 was related to abnormal development of stamen, including anther indehiscence and pollen abortion in KAM3315A plants. In addition, TaMYB305-silenced plants exhibited alterations in the transcriptional levels of genes involved in the synthesis of jasmonic acid (JA), indicating that TaMYB305 may regulate the expression of genes related to JA synthesis and play an important role during anther and pollen development of KTM3315A. These results provide novel insight into the function and molecular mechanism of R2R3-MYB genes in pollen development.

Cytological and transcriptomic analyses provide insights into the pollen fertility of synthetic allodiploid Brassica juncea hybrids.

Imbalanced chromosomes and cell cycle arrest, along with down-regulated genes in DNA damage repair and sperm cell differentiation, caused pollen abortion in synthetic allodiploid Brassica juncea hybrids. Interspecific hybridization is considered to be a major pathway for species formation and evolution in angiosperms, but the occurrence of pollen abortion in the hybrids is common, prompting us to recheck male gamete development in allodiploid hybrids after the initial combination of different genomes. Here, we investigated the several key meiotic and mitotic events during pollen development using the newly synthesised allodiploid B. juncea hybrids (AB, 2n=2× =18) as a model system. Our results demonstrated the partial synapsis and pairing of non-homologous chromosomes concurrent with chaotic spindle assembly, affected chromosome assortment and distribution during meiosis, which finally caused difference in genetic constitution amongst the final tetrads. The mitotic cell cycle arrest during microspore development resulted in the production of anucleate pollen cells. Transcription analysis showed that sets of key genes regulating cyclin (CYCA1;2 and CYCA2;3), DNA damage repair (DMC1, NBS1 and MMD1), and ubiquitin-proteasome pathway (SINAT4 and UBC) were largely downregulated at the early pollen meiosis stages, and those genes involved in sperm cell differentiation (DUO1, PIRL1, PIRL9 and LBD27) and pollen wall synthesis (PME48, VGDH11 and COBL10) were mostly repressed at the late pollen mitosis stages in the synthetic allodiploid B. juncea hybrids (AB). In conclusion, this study elucidated the related mechanisms affecting pollen fertility during male gametophyte development at the cytological and transcriptomic levels in the synthetic allodiploid B. juncea hybrids.

Cold-Tolerant and Short-Duration Rice (Oryza sativa L.) for Sustainable Food Security of the Flash Flood-Prone Haor Wetlands of Bangladesh

Rice cultivation in the low-lying basin-like wetlands, known as the Haor, is often affected by early flash floods during the first two weeks of April. The flooding is mainly caused by heavy rainfall and water surging downstream from the Meghalaya hills in India. This flash flood poses a significant threat to rice production, risking the country’s food security. Dry winter (Boro) rice is the primary food source throughout the year in the Haor region. Flash floods are the most catastrophic, affecting about 80% or even the entire rice yield. In 2017, a loss of 0.88 million metric tons of Boro rice in Haor regions cost the nation USD 450 million. To escape flash floods, it is recommended to sow Boro rice earlier, between the last week of October and the first week of November, instead of around 15 November so rice may be harvested by the last week of March before the onset of flash floods. However, early sowing has a possibility of causing grain sterility due to cold spells when the booting and heading stages of rice inevitably coincide with the cold period between 15 January and 7 February. The minimum temperature in the Haor regions ranges from 11 to 15 °C during this time. Rice is especially susceptible to low average temperatures (<20 °C) during the reproductive stage, leading to pollen abortion and the malformation of immature microspores. Low temperatures mainly impact rice cultivation in Haor regions during the reproductive phase, resulting in the degeneration of the spikelets, partial panicle exertion, and increased spikelet sterility, leading to a decrease in grain yield. Over two million hectares of Boro rice have been damaged by extreme cold spells in recent years, resulting in partial or total yield loss. To overcome the threats of flash floods and cold injury, breeding short-duration and cold-tolerant rice varieties is crucial. We assume that an economic benefit of USD 230 million per year could be achieved through the development and adoption of short-duration and cold-tolerant high-yielding rice varieties in the Haor regions of the country. In this review article, the authors summarized the problems and outline a way forward to overcome the flash flood and cold injury of Boro rice cultivation in the Haor districts of the country. Furthermore, the authors discussed the various forms and scenarios of cold damage and the global existence of cold-tolerant rice cultivars. Based on the available data from earlier research, a potential way of mitigating flash floods and cold devastation was suggested.

Growth and physiological response of canola (Brassica napus L.) tointeractive effect of temperature, moisture and nitrogen stressesunder controlled environment

Present atmospheric limits growth of C3 crop plants, which show response to elevated CO2 via reduced photorespiration and enhanced photosynthetic rates thereby increased growth and yield. Global research on plant responses to raising atmospheric CO2 has primarily focused on C3 species, advancing our understanding of processes underlying C3 plant acclimation and response. Therefore extensive research has been conducted to project the potential impacts of global warming on agriculture productivity through laboratory by using crop and global climate models. Canola is one of the world’s most important oilseed crops and the most profitable commodity for Canadian farmers. As a C3 cool seasoncrop, it is more susceptible to heat stress than other C3 and C4 field crops (Wu and Ma, 2018). High temperature significantly changes the rate of plant metabolic processes that ultimately reduces biomass accumulation and grainformation. A field study in Eastern Canada reported that seed yield reduced as much as 40% in 2012 due to severeheat and drought stress over normal years (Ma and Herath, 2016). High or warm temperature has been shown toinduce the floral sterility or pollen abortion and shorten seed filling duration and subsequently reduce inflorescence size in canola plants. Even high temperature could alter the partitioning of photoassimilates to roots and suppress root growth extension or change root system architecture. Late seeded canola plants often produced a smaller root system, due to higher temperature and or drought stress encounters during the crop development. Keeping these facts trial was conducted under controlled condition to know the response of canola to drought stress, elevated CO2 and temperature.

A P-type pentatricopeptide repeat protein ZmRF5 promotes 5' region partial cleavages of atp6c transcripts to restore the fertility of CMS-C maize by recruiting a splicing factor.

A fast evolution within mitochondria genome(s) often generates discords between nuclear and mitochondria, which is manifested as cytoplasmic male sterility (CMS) and fertility restoration (Rf) system. The maize CMS-C trait is regulated by the chimeric mitochondrial gene, atp6c, and can be recovered by the restorer gene ZmRf5. Through positional cloning in this study, we identified the nuclear restorer gene, ZmRf5, which encodes a P-type pentatricopeptide repeat (PPR) family protein. The over-expression of ZmRf5 brought back the fertility to CMS-C plants, whereas its genomic editing by CRISPR/Cas9 induced abortive pollens in the restorer line. ZmRF5 is sorted to mitochondria, and recruited RS31A, a splicing factor, through MORF8 to form a cleaving/restoring complex, which promoted the cleaving of the CMS-associated transcripts atp6c by shifting the major cleavage site from 480th nt to 344 th nt for fast degradation, and preserved just right amount of atp6c RNA for protein translation, providing adequate ATP6C to assembly complex V, thus restoring male fertility. Interestingly, ATP6C in the sterile line CMo17A, with similar cytology and physiology changes to YU87-1A, was accumulated much less than it in NMo17B, exhibiting a contrary trend in the YU87-1 nuclear genome previously reported, and was restored to normal level in the presence of ZmRF5. Collectively these findings unveil a new molecular mechanism underlying fertility restoration by which ZmRF5 cooperates with MORF8 and RS31A to restore CMS-C fertility in maize, complemented and perfected the sterility mechanism, and enrich the perspectives on communications between nucleus and mitochondria.