Apical Abortion Research Articles

Exploring the mechanism of blindness physiopathy in Brassica oleracea var italica L. by comprehensive transcriptomics and metabolomics analysis

Blindness is a physiopathy characterized by apical abortion that particularly affects the Brassica family. The occurrence of blindness has been related to exposure to low temperatures during early developmental stages. However, the causes of this selective sensitivity and how they affect the correct development remain unknown. In this study, we investigated the mechanisms involved in the occurrence of blindness in broccoli plants. The analysis of RNAseq, focused on membrane transporters and the synthesis pathways of glucosinolates and phenolics, was related with physiological changes in nutrient and water uptake, gas exchange, and metabolism. Comparative gene expression analysis between control and blindness-affected broccoli plants revealed distinct regulation patterns in roots and shoots, leading to reduced synthesis of glucosinolates and phenolics. Additionally, the expression levels of aquaporins and potassium transporters were found to be associated with mineral and water transport. In this way, our results revealed the causes of blindness by identifying differentially expressed genes, highlighting those related to secondary metabolism, as well as genes involved in water and nutrient uptake and transport as the crucial involved in the physiopathy appearance.

Panicle Apical Abortion 7 Regulates Panicle Development in Rice (Oryza sativa L.).

The number of grains per panicle significantly contributes to rice yield, but the regulatory mechanism remains largely unknown. Here, we reported a loss-of-function mutant, panicle apical abortion 7 (paa7), which exhibited panicle abortion and degeneration of spikelets on the apical panicles during the late stage of young panicle development in rice. High accumulations of H2O2 in paa7 caused programmed cell death (PCD) accompanied by nuclear DNA fragmentation in the apical spikelets. Map-based cloning revealed that the 3 bp “AGC” insertion and 4 bp “TCTC” deletion mutation of paa7 were located in the 3′-UTR regions of LOC_Os07g47330, which was confirmed through complementary assays and overexpressed lines. Interestingly, LOC_Os07g47330 is known as FRIZZY PANICLE (FZP). Thus, PAA7 could be a novel allele of FZP. Moreover, the severe damage for panicle phenotype in paa7/lax2 double mutant indicated that PAA7 could crosstalk with Lax Panicle 2 (LAX2). These findings suggest that PAA7 regulates the development of apical spikelets and interacts with LAX2 to regulate panicle development in rice.

LMPA Regulates Lesion Mimic Leaf and Panicle Development Through ROS-Induced PCD in Rice.

Leaf and panicle are important nutrient and yield organs in rice, respectively. Although several genes controlling lesion mimic leaf and panicle abortion have been identified, a few studies have reported the involvement of a single gene in the production of both the traits. In this study, we characterized a panicle abortion mutant, lesion mimic leaf and panicle apical abortion (lmpa), which exhibits lesions on the leaf and causes degeneration of apical spikelets. Molecular cloning revealed that LMPA encodes a proton pump ATPase protein that is localized in the plasma membrane and is highly expressed in leaves and panicles. The analysis of promoter activity showed that the insertion of a fragment in the promoter of lmpa caused a decrease in the transcription level. Cellular and histochemistry analysis indicated that the ROS accumulated and cell death occurred in lmpa. Moreover, physiological experiments revealed that lmpa was more sensitive to high temperatures and salt stress conditions. These results provide a better understanding of the role of LMPA in panicle development and lesion mimic formation by regulating ROS homeostasis.

Locus TUTOU2 determines the panicle apical abortion phenotype of rice (Oryza sativa L.) in tutou2 mutant

Rice panicle apical abortion (PAA) is a detrimental agronomic trait resulting in spikelet number reduction and yield loss. To understand its underlying molecular mechanism, we identified one recessive PAA mutant tutou2 from the offspring of tissue cultures. The mutation locus was finely mapped to a 75-kb interval on the long arm of chromosome 10. Sequence analysis revealed a single nucleotide substitution of A to T at the 941 position of LOC_Os10g31910 in tutou2, resulting in an amino acid change from isoleucine to phenylalanine. Complementation analysis showed that the degenerated panicle phenotype in tutou2 was rescued in the transgenic lines. A phenotype similar to tutou2 can also be obtained by LOC_Os10g31910 knockout in wild-type rice. These results suggested that LOC_Os10g31910 is the causative locus TUTOU2 responsible for the tutou2 PAA phenotype and probably also the locus of DEL1, previously documented as a leaf senescence gene. The significant phenotypic differences between del1 and tutou2 suggest that the locus DEL1/TUTOU2 plays roles in both leaf and panicle development which were not considered fully in previous studies.

Evidence of arrested silk growth in maize at high planting density using phenotypic and transcriptional analyses

Increasing the planting density is an effective way to increase the yield of maize (Zeamays L.), although it can also aggravate ovary apical abortion-induced bald tips of the ears, which might, in turn, reduce the yield. While the mechanism underlying the regulation of drought-related abortion in maize is well established, high planting density-related abortion in maize remains poorly understood.Therefore, the present study was designed to investigate the mechanism underlying the ovary apical abortion response to high density. This was achieved by evaluating the effects of four different plant densities (60000 plantsha−1 (60 k), 90 k, 120 k, and 150 k) on plant traits related to plant architecture, the plant ear, flowering time, and silk development in two inbred lines (Zheng58 and PH4CV) and two hybrid lines (Zhengdan958 and Xianyu335).The phenotypes of both inbred and hybrid plants were observed under different planting density treatments, and the high planting density was found to increase the phenotypic performance values of the evaluated traits. The anthesis–silking interval (ASI) was extended, and the amount of the silk extruded from husks was reduced upon increasing the planting density. Delayed silk emergence resulted in asynchronous flowering and ear bald tips. Observations of the silk cells revealed that the silk cells became smaller as planting density increased.The changes in transcript abundances in the silks involved the genes associated with expansive growth rather than carbon metabolism. These findings further our understanding of silk growth regulation under high planting density and provide a theoretical basis for further research on improving high planting density breeding in maize.

Panicle Apical Abortion 3 Controls Panicle Development and Seed Size in Rice

BackgroundIn rice, panicle apical abortion is a common phenomenon that usually results in a decreased number of branches and grains per panicle, and consequently a reduced grain yield. A better understanding of the molecular mechanism of panicle abortion is thus critical for maintaining and increasing rice production.ResultsWe reported a new rice mutant panicle apical abortion 3 (paa3), which exhibited severe abortion of spikelet development on the upper part of the branches as well as decreased grain size over the whole panicle. Using mapping-based clone, the PAA3 was characterized as the LOC_ Os04g56160 gene, encoding an H+-ATPase. The PAA3 was expressed highly in the stem and panicle, and its protein was localized in the plasma membrane. Our data further showed that PAA3 played an important role in maintaining normal panicle development by participating in the removal of reactive oxygen species (ROS) in rice.ConclusionsOur studies suggested that PAA3 might function to remove ROS, the accumulation of which leads to programmed cell death, and ultimately panicle apical abortion and decreased seed size in the paa3 panicle.

Fine Mapping of a Novel Major Quantitative Trait Locus, qPAA7, That Controls Panicle Apical Abortion in Rice.

The panicle apical abortion (PAA) causes severe yield losses in rice production, but details about its development and molecular basis remain elusive. Here, we detected PAA quantitative trait loci (QTLs) in three environments using a set of chromosome segment substitution lines (CSSLs) that was constructed with indica Changhui121 as the recurrent parent and japonica Koshihikari as the donor parent. First, we identified a novel major effector quantitative trait locus, qPAA7, and selected a severe PAA line, CSSL176, which had the highest PAA rate among CSSLs having Koshihikari segments at this locus. Next, an F2 population was constructed from a cross between CSS176 and CH121. Using F2 to make recombinantion analysis, qPAA7 was mapped to an 73.8-kb interval in chromosome 7. Among nine candidate genes within this interval, there isn’t any known genes affecting PAA. According to the gene annotation, gene expression profile and alignment of genomic DNA, LOC_Os07g41220 and LOC_Os07g41280 were predicted as putative candidate genes of qPAA7. Our study provides a foundation for cloning and functional characterization of the target gene from this locus.

Rice Calcineurin B-Like Protein-Interacting Protein Kinase 31 (OsCIPK31) Is Involved in the Development of Panicle Apical Spikelets.

Panicle apical abortion (PAA) causes severe yield losses in rice production, but details about its development and molecular basis remain elusive. Herein, a PAA mutant, paa1019, was identified among the progeny of an elite indica maintainer rice line Yixiang 1B (YXB) mutagenized population obtained using ethyl methyl sulfonate. The abortion rate of spikelets in paa1019 was observed up to 60%. Genetic mapping combined with Mutmap analysis revealed that LOC_Os03g20380 harbored a single-bp substitution (C to T) that altered its transcript length. This gene encodes calcineurin B-like protein-interacting protein kinase 31 (OsCIPK31) localized into the cytoplasm, and is preferentially expressed in transport tissues of rice. Complementation of paa1019 by transferring the open reading frame of LOC_Os03g20380 from YXB reversed the mutant phenotype, and conversely, gene editing by knocking out of OsCIPK31 in YXB results in PAA phenotype. Our results support that OsCIPK31 plays an important role in panicle development. We found that dysregulation is caused by the disruption of OsCIPK31 function due to excessive accumulation of ROS, which ultimately leads to cell death in rice panicle. OsCIPK31 and MAPK pathway might have a synergistic effect to lead ROS accumulation in response to stresses. Meanwhile the PAA distribution is related to IAA hormone accumulation in the panicle. Our study provides an understanding of the role of OsCIPK31 in panicle development by responding to various stresses and phytohormones.

Identification and gene mapping of a panicle apical abortion mutant (<italic>paa1331</italic>) in rice

Rice panicle is an important agronomic organ which influences yield, and its development directly determines the yield potential. Over the past decades, a large number of genes related to grain size and grain number have been cloned, but there are few reports on cloning and function characterization of genes related to panicle development. We aim to explore the genes that regulate the degeneration of rice spike, improve the regulation network of panicle development, and provide theoretical basis for molecular breeding. In this study, a stably inherited mutant showing perturbed development of panicle ( panicle apical abortion 1331 ) was isolated from an ethyl methyl sulfate(EMS)mutagenized population of Yixiang 1B. Compared with the wild type, the mutant mainly showed a severe degeneration at the panicle tip (the affected florets account for as high as 53%), in addition to this, the plant height, tiller number and grain number were also affected. Observation on the development of panicle showed that the top spikelets of mutant paa1331 began to degrade during meiosis of the pollen mother cell, and the number of degenerated spikelets increased with the elongation of the young spike, distributing at the top of the first branch of the stem, while the number of degenerated spikelets showed a tendency to decrease gradually from top to bottom. Anatomical observations showed that the stamens of the mutant degenerated spikelets degenerated into linear, and the pulp was withered. The tissue section of mutant paa1331 and pollen staining assay showed that there were no pollen grains in the mutant anther, indicating that degeneration hindered the development of pollen; the vascular bundle of the mutant degenerated stem showed developmental defects, which may cause the transport of the material to be obstructed Trypan blue staining assay showed severe coloration of degraded spikelets on top of mutants, indicted that the panicle apical abortion was associated with programmed cell death. Hormone assay suggested that the IAA content of mutants was higher than that of wild type. Genetic analysis showed that mutant trait was controlled by a recessive gene. Combined the analysis of map-based cloning and De novo genome sequencing, we found one gene LOC_Os04g40720 , of which the fourth exon has an A-to-G single base substitution, which resulted in a change from Asn to Asp. At present, this gene has not been reported to confer function in panicle development, thus we treated it as candidate gene.

SPL6 represses signalling outputs of ER stress in control of panicle cell death in rice.

Inositol-requiring enzyme 1 (IRE1) is the most conserved transducer of the unfolded protein response that produces either adaptive or death signals depending on the amplitude and duration of its activation. Here, we report that SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 6 (SPL6)-deficient plants displayed hyperactivation of the endoplasmic reticulum (ER) stress sensor IRE1, leading to cell death in rice panicles, indicating that SPL6 is an essential survival factor for the suppression of persistent or intense ER stress conditions. Importantly, knockdown of the hyperactivated mRNA level of IRE1 rescues panicle apical abortion in the spl6-1 transgenic plants harbouring the IRE1-RNAi constructs, establishing the genetic linkage between the hyperactivation of IRE1 and cell death in spl6-1. Our findings reveal a novel cell survival machinery in which SPL6 represses the transcriptional activation of the ER stress sensor IRE1 in control of ER stress signalling outputs that hinge on a balance between adaptive and death signals for determining cell fates during ER stress.

Ovary Apical Abortion under Water Deficit Is Caused by Changes in Sequential Development of Ovaries and in Silk Growth Rate in Maize.

Grain abortion allows the production of at least a few viable seeds under water deficit but causes major yield loss. It is maximum for water deficits occurring during flowering in maize (Zea mays). We have tested the hypothesis that abortion is linked to the differential development of ovary cohorts along the ear and to the timing of silk emergence. Ovary volume and silk growth were followed over 25 to 30 d under four levels of water deficit and in four hybrids in two experiments. A position-time model allowed characterizing the development of ovary cohorts and their silk emergence. Silk growth rate decreased in water deficit and stopped 2 to 3 d after first silk emergence, simultaneously for all ovary cohorts, versus 7 to 8 d in well-watered plants. Abortion rate in different treatments and positions on the ear was not associated with ovary growth rate. It was accounted for by the superposition of (1) the sequential emergence of silks originating from ovaries of different cohorts along the ear with (2) one event occurring on a single day, the simultaneous silk growth arrest. Abortion occurred in the youngest ovaries whose silks did not emerge 2 d before silk arrest. This mechanism accounted for more than 90% of drought-related abortion in our experiments. It resembles the control of abortion in a large range of species and inflorescence architectures. This finding has large consequences for breeding drought-tolerant maize and for modeling grain yields in water deficit.

Fine mapping and candidate gene analysis of a new mutant gene for panicle apical abortion in rice

The rice panicle architecture depends on the arrangement of branches and spikelets which directly affect grain yield. We identified a mutant for panicle apical abortion (PAA-Hwa) from a japonica cultivar Hwacheongbyeo treated with N-methyl-N-nitrosourea. Under normal growth conditions, the mutant had multiple abnormal phenotypes, such as a slight reduction in plant height, narrow and dark green leaf blades, and small erect panicles with clear PAA compared to the wild-type plants. Genetic analysis revealed that the PAA was controlled by a single recessive gene, which is tentatively designated as paa-h. The paa-h gene was fine mapped at an interval of 71 kb flanked by sequence tagged site markers aptn3 and S6685-1 at the long arm of chromosome 4. Sequence analysis of the candidate genes within the delimited region showed a single base-pair change corresponding to an amino acid substitution from glycine to glutamic acid at the candidate gene, LOC_Os04g56160. We expect that the paa-h gene will be a clue to uncover the molecular mechanism of PAA and to maintain the panicle identity for grain yield in rice breeding programs.

Genetic Analysis of Rice Mutant <I>L-05261</I> with Panicle Apical Abortion Trait

Genetic Analysis of Rice Mutant <I>L-05261</I> with Panicle Apical Abortion Trait

Fine Mapping of qPAA8, a Gene Controlling Panicle Apical Development in Rice

In rice, one detrimental factor influencing single panicle yield is the frequent occurrence of panicle apical abortion (PAA) under unfavorable climatic conditions. Until now, no detailed genetic information has been available to avoid PAA in rice breeding. Here, we show that the occurrence of PAA is associated with the accumulation of excess hydrogen peroxide. Quantitative trait loci (QTLs) mapping for PAA in an F(2) population derived from the cross of L-05261 (PAA line) × IRAT129 (non-PAA variety) identified seven QTLs over a logarithm of the odd (LOD) threshold of 2.5, explaining approximately 50.1% of phenotypic variance for PAA in total. Five of the QTLs with an increased effect from L-05261, were designated as qPAA3-1, qPAA3-2, qPAA4, qPAA5 and qPAA8, and accounted for 6.8%, 5.9%, 4.2%, 13.0% and 12.2% of phenotypic variance, respectively. We found that the PAA in the early heading plants was mainly controlled by qPAA8. Subsequently, using the sub-populations specific for qPAA8 based on marker-assisted selection, we further narrowed qPAA8 to a 37.6-kb interval delimited by markers RM22475 and 8-In112. These results are beneficial for PAA gene clone.

Apical abortion in calabrese is induced by periods of low temperature and results in premature differentiation of apical meristem cells

Apical abortion in calabrese (Brassica oleracea var. italica), a highly destructive disorder which occurs in overwintered transplants, has been investigated using a model system in which blindness (abortion of the apical meristem) can be reproducibly and predictably induced. An initial experiment examined the susceptibility of 12 cultivars to apical abortion when grown throughout a winter period under commercial conditions. Three of those varieties showed very high levels of blindness (100%). Subsequently, plants of the susceptible cultivar PETO 7204 were subjected to an inductive period of low light intensity (30 μmol m -2 s -1 ) and low temperature (4°C). Apical meristematic cells of all plants ceased mitotic activity within 3 d of being transferred to a regime comprising higher light intensity (100 μmol m -2 s -1 ) and temperature (15°C). Using this system the structures of normal apices were compared with those which became blind. Blindness was characterized by a cessation of leaf primordium production by the vegetative apex, the last formed primordium growing on in some cases to form a mature normal leaf, or in others, a deformed structure known as a whip-tail. The inactive apical bud became embedded in the tissues of this last-formed structure. The cells of the inactivated apical bud remained alive, but lost their meristematic capability, becoming enlarged, highly vacuolated parenchyma cells with amyloplasts.

Apical abortion in calabrese is induced by periods of low temperature and results in premature differentiation of apical meristem cells

Apical abortion in calabrese is induced by periods of low temperature and results in premature differentiation of apical meristem cells

The effects of radiation frost on freezing damage and apical abortion in calabrese (Brassica oleracea var. italica) transplants

SummaryFreezing damage has been reported to be associated with apical abortion (blindness) in calabrese, preventing the formation of a marketable head. In the past, laboratory based experiments studying the freezing of whole plants using convective freezing have resulted in death of the plants while failing to induce blindness. Using a unique radiation freezing facility, capable of reproducibly simulating glasshouse frost conditions, we investigated the effect of hardening and freezing duration on calabrese transplants. Four cultivars were raised and subjected at four different growth stages (3, 5, 7 and 9 leaves) to a factorial combination of frost (0-4 d of frost between 22 to 248C) and hardening regimes (0-6 d at 48C prior to freezing). Following each frost/hardening treatment, half the sample was dissected and the remainder potted up and grown on. Light and transmission electron microscopy of the dissected plants revealed that the apical region of all the varieties at each of the growth stages remained intact following all frost treatments applied. No significant apical abortion was recorded. No blind plants were recorded following a repeat of the experiment using commercially grown plants (cv. Marathon). It was observed that the apical region of the calabrese transplants has a high degree of frost tolerance and that freezing conditions alone are not responsible for the induction of apical abortion.

Vegetative and reproductive development of the Montana blue huckleberry (Vaccinium globulare Rydb.)

SummaryThe Montana blue huckleberry (Vaccinium globulare Rydb.) is a popular and highly sought wild fruit in the western United States. Because it is becoming increasingly difficult to meet growing market demands from wild harvests, growers and state officials are funding projects to investigate cultivation of the fruit. This study investigates the vegetative and reproductive growth patterns of this species as a prelude to its cultivation. Such information is critical in properly scheduling fertilizing, pruning and other cultural practices. The species produces fixed sympodial, non-episodic vegetative extension growth over a four-week period each season, followed by apical abortion and the formation of vegetative or mixed buds. Floret differentiation begins shortly after cessation of shoot growth and all floral parts are differentiated by late summer of the year prior to anthesis.

The effects of shade on shoot growth of Vaccinium angustifolium Ait. after fire pruning in southeastern Manitoba

Five plots (15 m × 0.3 m) containing similar numbers of Vaccinium angustifolium shoots were laid out within a clearing in a natural Pinus banksiana stand. The area was burned in late April. Wooden screens were then erected to provide 0,25, 50,75, and 100% shade over the plots. Growth of blueberries and competing vegetation was monitored throughout the growing season using 10 quadrats (930 cm2) per plot. Soil characteristics, temperature, moisture, and light were measured.Quadrats with low preburn densities showed a greater increase in shoot numbers than those with high densities, regardless of shade. The times of shoot emergence and apical abortion were also independent of shade. Other blueberry characteristics were influenced by shade. Shoot density, shoot branching, and number of branches per shoot were highest in the open; frost damage was also greatest.However, blueberries under intermediate shade grew faster, had larger leaves, longer and stouter shoots, and experienced a more favorable water economy. In general, shade, considered detrimental to blueberries in the Atlantic Provinces, may be essential for optimal growth in Manitoba's continental climate.

Growth and Development of Highbush Blueberry. I. Vegetative Growth

Abstract The seasonal vegetative growth sequences of the highbush blueberry (Vaccinium corymbosum Ait.) and certain features, including apical abortion, are described during growth under usual conditions and under the influence of succinic acid-2,2-dimethylhydrazide (daminozide) sprays. Apical abortion, followed by chlorosis and necrosis of the distal portion of the shoot is a natural phenomenon in highbugh blueberry and results in episodic, sympodial extension growth. Daminozide sprays did not substantially alter the abortion pattern, though shoot growth was substantially reduced the first year of spray application. Shoot growth was not significantly reduced in bushes sprayed but not pruned for 2 years.