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The HUELLENLOS (HLL) gene participates in patterning and growth of the Arabidopsis ovule. We have isolated the HLL gene and shown that it encodes a protein homologous to the L14 proteins of eubacterial ribosomes. The Arabidopsis genome also includes a highly similar gene, HUELLENLOS PARALOG (HLP), and genes for both cytosolic (L23) and chloroplast...
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Context 1
... overlapping cosmid subclones from BAC T24L7 that complemented the hll-1 mutation are depicted in Figure 2. Segregation analysis in the progeny of these plants con- the complementation, because the transgenes al- ways cosegregated with a wild-type phenotype in hll-1 homozygotes (data not shown). ...
Context 2
... 16-kb region of overlap between the complementing cosmids was sequenced from cosmid T24L7-143, and two candidate protein coding regions (designated A and B) and a putative tRNA gene were identified (Figure 2). Polymerase chain reaction (PCR) products for each putative gene were amplified from hll-1 and hll-2 genomic DNA and sequenced to compare with wild-type genomic sequences of Landsberg erecta and Columbia. ...
Similar publications
When mutations in CUP-SHAPED COTYLEDON1 (CUC1) and CUC2 are combined, severe defects involving fusion of sepals and of stamens occur in Arabidopsis flowers. In addition, septa of gynoecia do not fuse along the length of the ovaries and many ovules have their growth arrested. CUC2 is expressed at the tips of septal primordia during gynoecium develop...
Citations
... Some regulators affecting integument development also affect ovule primordia initiation, such as HUELLENLOS (HLL) and SHORT INTEGUMENTS 2 (SIN2) (Schneitz et al., 1998;Broadhvest et al., 2000). HLL encodes a mitochondrial ribosomal protein whose mutation is associated with a 10% reduction in ovule number (Schneitz et al., 1998;Skinner et al., 2001). SIN2 encodes a mitochondrial DAR GTPase. ...
Seed is the offspring of angiosperms. Plants produce large numbers of seeds to ensure effective reproduction and survival in varying environments. Ovule is a fundamentally important organ and is the precursor of the seed. In Arabidopsis and other plants characterized by multi‐ovulate ovaries, ovule initiation determines the maximal ovule number, thus greatly affecting seed number per fruit and seed yield. Investigating the regulatory mechanism of ovule initiation has both scientific and economic significance. However, the genetic and molecular basis underlying ovule initiation remains unclear due to technological limitations. Very recently, rules governing the multiple ovules initiation from one placenta have been identified, the individual functions and crosstalk of phytohormones in regulating ovule initiation have been further characterized, and new regulators of ovule boundary are reported, therefore expanding the understanding of this field. In this review, we present an overview of current knowledge in ovule initiation and summarize the significance of ovule initiation in regulating the number of plant offspring, as well as raise insights for the future study in this field that provide potential routes for the improvement of crop yield.
... Most mitochondrial ribosomal proteins are encoded by the nuclear genome, synthesized in the cytoplasm and transported into mitochondria (Unseld et al., 1997). Loss of mitochondrial ribosomal proteins leads to specific developmental defects such as embryonic lethality, abnormal leaf morphology and defective formation of reproductive structures (Skinner et al., 2001;Portereiko et al., 2006;Van Aken et al., 2007;Zhou et al., 2011;Kwasniak et al., 2013;Pineau et al., 2013;Deng et al., 2014;Zhang et al., 2015). ...
Protein bodies (PBs), the major protein storage organelle in maize (Zea mays) endosperm, comprise zeins and numerous nonzein proteins (NZPs). Unlike zeins, how NZPs accumulate in PBs remains unclear.
We characterized a maize miniature kernel mutant, mn*, that produces small kernels and is embryo‐lethal. After cloning the Mn* locus, we determined that it encodes the mitochondrial 50S ribosomal protein L10 (mRPL10). MN* localized to mitochondria and PBs as an NZP; therefore, we renamed MN* Non‐zein Protein 1 (NZP1). Like other mutations affecting mitochondrial proteins, mn* impaired mitochondrial function and morphology.
To investigate its accumulation mechanism to PBs, we performed protein interaction assays between major zein proteins and NZP1, and found that NZP1 interacts with 22 kDa α‐zein. Levels of NZP1 and 22 kDa α‐zein in various opaque mutants were correlated. Furthermore, NZP1 accumulation in induced PBs depended on its interaction with 22 kDa α‐zein. Comparative proteomic analysis of PBs between wild‐type and opaque2 revealed additional NZPs. A new NZP with plastidial localization was also found to accumulate in induced PBs via interaction with 22 kDa α‐zein.
This study thus reveals a mechanism for accumulation of NZPs in PBs and suggests a potential application for the accumulation of foreign proteins in maize PBs.
... Mitochondria are important with regards to sensing and integrating signals, stress responses and plant development [20]. Reproductive development is severely sensitive to mitochondrial mutations, which affect mitochondrial functions [21,22]. However, molecular and genetic mechanisms behind mitochondrial activity and regulation during plant development are still mostly uncharacterized. ...
Background:
Flowering is a crucial stage during plant development. Plants may respond to unfavorable conditions by accelerating reproductive processes like flowering. In a recent study, we showed that PRECOCIOUS1 (POCO1) is a mitochondrial pentatricopeptide repeat (PPR) protein involved in flowering time and abscisic acid (ABA) signaling in Arabidopsis thaliana. Here, we use RNA-seq data to investigate global gene expression alteration in the poco1 mutant.
Results:
RNA-seq analysis was performed during different developmental stages for wild-type and poco1 plants. The most profound differences in gene expression were found when wild-type and poco1 plants of the same developmental stage were compared. Coverage analysis confirmed the T-DNA insertion in POCO1, which was concomitant with truncated transcripts. Many biological processes were found to be enriched. Several flowering-related genes such as FLOWERING LOCUS T (FT), which may be involved in the early-flowering phenotype of poco1, were differentially regulated. Numerous ABA-associated genes, including the core components of ABA signaling such as ABA receptors, protein phosphatases, protein kinases, and ABA-responsive element (ABRE) binding proteins (AREBs)/ABRE-binding factors (ABFs) as well as important genes for stomatal function, were mostly down-regulated in poco1. Drought and oxidative stress-related genes, including ABA-induced stress genes, were differentially regulated. RNA-seq analysis also uncovered differentially regulated genes encoding various classes of transcription factors and genes involved in cellular signaling. Furthermore, the expression of stress-associated nuclear genes encoding mitochondrial proteins (NGEMPs) was found to be altered in poco1. Redox-related genes were affected, suggesting that the redox state in poco1 might be altered.
Conclusion:
The identification of various enriched biological processes indicates that complex regulatory mechanisms underlie poco1 development. Differentially regulated genes associated with flowering may contribute to the early-flowering phenotype of poco1. Our data suggest the involvement of POCO1 in the early ABA signaling process. The down-regulation of many ABA-related genes suggests an association of poco1 mutation with the ABA signaling deficiency. This condition further affects the expression of many stress-related, especially drought-associated genes in poco1, consistent with the drought sensitivity of poco1. poco1 mutation also affects the expression of genes associated with the cellular regulation, redox, and mitochondrial perturbation.
... From studies of inflorescences with stages 1-12 flowers, the expression of the outer integument growth-regulating genes ANT and HUELLENLOS (HLL) are regulated by BR signaling (Huang et al. 2013). Because ANT and HLL are also involved in regulating flower or gynoecium development (Klucher et al. 1996;Skinner et al. 2001), the use of whole inflorescences for qRT-PCR made it difficult to determine where this BR-regulated expression of ANT and HLL actually occurred in the ovules. In our study, using isolated ovules as material, both qRT-PCR and RNA-seq results indicated that among genes previously reported to regulate outer integument growth (ANT, HLL, INO, SIN1, SUP, and BEL1), only the expression of INO was downregulated in bri1-116 ovules, and it was restored to a wild-type level by the bzr1-1D mutation. ...
Brassinosteroids (BRs) play important roles in regulating plant reproductive processes. BR signaling or BR biosynthesis null mutants do not produce seeds under natural conditions, but the molecular mechanism underlying this infertility is poorly understood. In this study, we report that outer integument growth and embryo sac development were impaired in the ovules of the Arabidopsis thaliana BR receptor null mutant bri1‐116. Gene expression and RNA‐seq analyses showed that the expression of INNER NO OUTER (INO), an essential regulator of outer integument growth, was significantly reduced in the bri1‐116 mutant. Increased INO expression due to overexpression or increased transcriptional activity of BRASSINAZOLE‐RESISTANT 1 (BZR1) in the mutant alleviated the outer integument growth defect in bri1‐116 ovules, suggesting that BRs regulate outer integument growth partially via BZR1‐mediated transcriptional regulation of INO. Meanwhile, INO expression in bzr‐h, a null mutant for all BZR1 family genes, was barely detectable; and the outer integument of bzr‐h ovules had much more severe growth defects than those of the bri1‐116 mutant. Together, our findings establish a new role for BRs in regulating ovule development and suggest that BZR1 family transcription factors might regulate outer integument growth through both BRI1‐dependent and BRI1‐independent pathways.
... Two examples are HUELLENLOS (HLL) and SHORT INTEGUMENTS 2 (SIN2). HLL encodes a mitochondrial ribosomal protein and its mutation is associated with smaller gynoecia and a 10% reduction in the number of ovules Skinner et al., 2001). Shorter gynoecia that bear fewer ovules are also observed in the sin2 mutant; however, more interestingly, the absence of SIN2 function leads to an abnormal distribution of ovules along the placenta (Broadhvest et al., 2000), in which the distance between ovules is greater than in the wild-type; thus, a reduction in ovule number is caused by a reduction in gynoecium size and by the reduced ability of the placental tissue to initiate ovule primordia. ...
Angiosperms form the biggest group of land plants and display an astonishing diversity of floral structures. The development of the flowers greatly contributed to the evolutionary success of the angiosperms as they guarantee efficient reproduction with the help of either biotic or abiotic vectors. The female reproductive part of the flower is the gynoecium (also called pistil). Ovules arise from meristematic tissue within the gynoecium. Upon fertilization, these ovules develop into seeds while the gynoecium turns into a fruit. Gene regulatory networks involving transcription factors and hormonal communication regulate ovule primordium initiation, their spacing on the placenta, and ovule development. Ovule number and gynoecium size are usually correlated and several genetic factors that impact these traits have been identified. Understanding and fine-tuning the gene regulatory networks influencing ovule number and pistil length opens up strategies for crop yield improvement, which is pivotal in light of a rapidly growing world population. In this review, we present an overview of the current knowledge of the genes and hormones involved in determining ovule number and gynoecium size. We propose a model for the gene regulatory network that guides the developmental processes that determine seed yield.
... Most mitochondrial ribosomal proteins are encoded by genes in the nucleus, imported into the mitochondrial matrix, and involved in mitochondrial ribosome assembly for translation (Unseld et al., 1997). A growing body of evidence shows that mutations in some nuclear genes encoding mitochondrially targeted proteins lead to specific developmental phenotypes (Skinner et al., 2001;Portereiko et al., 2006;Van Aken et al., 2007;Zhou et al., 2011;Kwasniak et al., 2013;Pineau et al., 2013;Deng et al., 2014;Pan et al., 2014;Zhang et al., 2015b). Some of these mutations occur in the genes encoding mitochondrial ribosomal proteins. ...
... Starting at stage 2, ANT is expressed in the chalaza and integuments primordia where it is speculated to regulate cell proliferation underlying integument outgrowth [16,49]. Furthermore, ANT and the mitochondrial ribosomal protein HUELLENLOS (HLL) have redundant functions in establishing the ovule proximal-distal axis [73,79]. Ipomorph hll alleles display early arrest of integument development and, in combination with ant mutations, lead to reduced chalaza and funiculus regions [73]. ...
The seed habit represents a remarkable evolutionary advance in plant sexual reproduction. Since the Paleozoic, seeds carry a seed coat that protects, nourishes and facilitates the dispersal of the fertilization product(s). The seed coat architecture evolved to adapt to different environments and reproductive strategies in part by modifying its thickness. Here, we review the great natural diversity observed in seed coat thickness among angiosperms and its molecular regulation in Arabidopsis.
... Early cellular degeneration of the eggs, characterised by arrested ovule development before or just after the formation of the integuments (hll-1) or after the integuments have begun to spread around the nucela (hll-2). hll-1 and hll-2 also show alterations in the gynoecium [23] NUCLEAR FUSION DEFECTIVE1 (NFD1) b AT4G30925 d L21 Arabidopsis thaliana Defective in kariogamy during fertilization and development of the female and male gametophytes [24] NFD3 b AT1G31817 d S11 Arabidopsis thaliana Defective in kariogamy during fertilization and development of the female gametophyte [24] Vegetative development rps3 c and rpl16 c S3 and L16 Zea mays Sectors of poorly developed tissue on leaves and ears, which result from the segregation of somatic wild-type and mutant mitochondria [25] rps3 c and rpl16 c AtMg00090 d and AtMg00080 d S3 and L16 Arabidopsis thaliana Distorted leaf phenotype [26] Rps10 b AT3G22300 d S10 Arabidopsis thaliana ...
... The characterisation of plant mutants has revealed a role for some mitoRPs in reproductive tissue formation. Along these lines, the Arabidopsis huellenlos-1 (hll-1) and hll-2 mutants are good representatives ( Table 1) [23]. hll-1 and hll-2 individuals carry point mutations which lead to truncated L14 mitoribosomal proteins and cause arrested ovule development before or immediately after the formation of integuments of ovules (hll-1), or after integuments have begun to spread around the nucela (hll-2) [23]. ...
... Along these lines, the Arabidopsis huellenlos-1 (hll-1) and hll-2 mutants are good representatives ( Table 1) [23]. hll-1 and hll-2 individuals carry point mutations which lead to truncated L14 mitoribosomal proteins and cause arrested ovule development before or immediately after the formation of integuments of ovules (hll-1), or after integuments have begun to spread around the nucela (hll-2) [23]. hll-1 and hll-2 also present alterations in the gynoecium, which is smaller than in the wild type and has a few ovules. ...
Mitochondria are the powerhouse of eukaryotic cells because they are responsible for energy production through the aerobic respiration required for growth and development. These organelles harbour their own genomes and translational apparatus: mitochondrial ribosomes or mitoribosomes. Deficient mitochondrial translation would impair the activity of this organelle, and is expected to severely perturb different biological processes of eukaryotic organisms. In plants, mitoribosomes consist of three rRNA molecules, encoded by the mitochondrial genome, and an undefined set of ribosomal proteins (mitoRPs), encoded by nuclear and organelle genomes. A detailed functional and structural characterisation of the mitochondrial translation apparatus in plants is currently lacking. In some plant species, presence of small gene families of mitoRPs whose members have functionally diverged has led to the proposal of the heterogeneity of the mitoribosomes. This hypothesis supports a dynamic composition of the mitoribosomes. Information on the effects of the impaired function of mitoRPs on plant development is extremely scarce. Nonetheless, several works have recently reported the phenotypic and molecular characterisation of plant mutants affected in mitoRPs that exhibit alterations in specific development aspects, such as embryogenesis, leaf morphogenesis or the formation of reproductive tissues. Some of these results would be in line with the ribosomal filter hypothesis, which proposes that ribosomes, besides being the machinery responsible for performing translation, are also able to regulate gene expression. This review describes the phenotypic effects on plant development displayed by the mutants characterised to date that are defective in genes which encode mitoRPs. The elucidation of plant mitoRPs functions will provide a better understanding of the mechanisms that control organelle gene expression and their contribution to plant growth and morphogenesis.
... In the 'Ribosome' subclass, the non-MLR mRNA with the lower log 2 Ratio (PGSC0003DMG403005640, log 2 Ratio À4.5; Figure S4) was verified as correctly annotated as ribosomal in St and for its At orthologue (MRPL14 family). However, the At gene has been shown to be overexpressed in pistils and essential for ovule development (Skinner et al., 2001), suggesting that the protein has a regulatory role rather than being an invariable component of the core mitoribosome (Janska and Kwasniak, 2014). Such a result has been suggested by analysis of the log 2 Ratio. ...
Intracellular sorting of mRNAs is an essential process to regulate gene expression and protein localization. Most of mitochondrial proteins are nuclear-encoded and imported into mitochondria, through post-translational or co-translational processes. In the latter case, mRNAs are found enriched in the vicinity of mitochondria. A genome-scale analysis of mRNAs associated with mitochondria has been performed to determine plant cytosolic mRNAs targeted to the mitochondrial surface. Many messengers encoding mitochondrial proteins were found associated with mitochondria. These mRNAs correspond to particular functions and complexes such as respiration or mitoribosomes, which indicates a coordinated control of mRNAs localization within metabolic pathways. In addition, upstream AUGs in 5′-UTR, which modulate translation efficiency of downstream sequences, were found to negatively affect mRNAs association with mitochondria. A mutational approach coupled with in vivo mRNA visualization confirmed this observation. Moreover, this technic allowed the identification of 3′-UTR as another essential element for mRNA localization at the mitochondrial surface. Therefore, this work offers new insights into the mechanism, function and regulation of cytosolic mRNAs association with plant mitochondria.
... Mutations causing mitochondrial defects do not necessarily have to be in mitochondrial-encoded genes, but can also reside in nuclear-encoded genes with mitochondrial function [152,153]. An example is female sterility caused by mutation in the nuclear-encoded gene Hüllenlos (HLL), encoding a mitochondrial ribosomal subunit [154]. ...
Eukaryotic cells require orchestrated communication between nuclear and organellar genomes, perturbations in which are linked to stress response and disease in both animals and plants. In addition to mitochondria, which are found across eukaryotes, plant cells contain a second organelle, the plastid. Signaling both among the organelles (cytoplasmic) and between the cytoplasm and the nucleus (i.e. nuclear-cytoplasmic interactions (NCI)) is essential for proper cellular function. A deeper understanding of NCI and its impact on development, stress response, and long-term health is needed in both animal and plant systems. Here we focus on the role of plant mitochondria in development and stress response. We compare and contrast features of plant and animal mitochondrial genomes (mtDNA), particularly highlighting the large and highly dynamic nature of plant mtDNA. Plant-based tools are powerful, yet underutilized, resources for enhancing our fundamental understanding of NCI. These tools also have great potential for improving crop production. Across taxa, mitochondria are most abundant in cells that have high energy or nutrient demands as well as at key developmental time points. Although plant mitochondria act as integrators of signals involved in both development and stress response pathways, little is known about plant mtDNA diversity and its impact on these processes. In humans, there are strong correlations between particular mitotypes (and mtDNA mutations) and developmental differences (or disease). We propose that future work in plants should focus on defining mitotypes more carefully and investigating their functional implications as well as improving techniques to facilitate this research.
