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Abstract: Sorghum is one of the pioneering cereal crops where cytoplasmic male sterility (CMS) was successfully exploited for mass production of F1 hybrid seed. Mapping genes for fertility restoration (Rf) is an important aspect of understanding the molecular basis of fertility restoration in crop plants. In this study, we fine‐mapped a fertility restoration locus, Rf2 of sorghum reported earlier (Jordan, Mace, Henzell, Klein, & Klein, ), involving two F2 populations (296A × RS29 and 296A × DSV1) and newly developed SSR markers delimited Rf2 locus to 10.32‐kb region on chromosome 2. The Rf2 locus was tightly linked with two new SSRs, MS‐SB02‐3460 (0.14 cM) and MS‐SB02‐3466 (0.75 cM) on both sides, and hosted only one gene (Sobic.002G057050) of PPR gene family. Another new SSR marker developed in the study, MS‐SB02‐37912, forms the part of PPR gene and could act as a perfect marker in marker‐assisted breeding for fertility restoration involving Rf2 in sorghum breeding. The strong involvement of Sobic.002G057050 gene in fertility restoration was supported through RNA expression analysis. [ABSTRACT FROM AUTHOR]

Abstract: Adoption of pigeonpea hybrids in central and southern India is showing high impact with on‐farm yield advantages of >30%. The hybrid pigeonpea technology, the first in any legume crop, is based on a cytoplasmic‐nuclear male‐sterility (CMS) system. For a long‐term sustainability of hybrid programme, it is imperative that both nuclear diversity and cytoplasmic diversity are maintained among hybrid parents. In this context, a continuous search for new CMS‐inducing cytoplasms is necessary. This paper reports detection of maternal inheritance of male sterility in the progeny derived from a natural hybrid between a wild relative [Cajanus lineatus (W. & A.) Maesen comb. nov.] of pigeonpea and an unknown pigeonpea [Cajanus cajan (L.) Millsp.] genotype. In the present study, the male sterility was maintained up to BC7F1 generation by an advanced breeding pigeonpea line ICPL 99044. This male sterility inducing cytoplasm of C. lineatus was tagged as A6. In future, this CMS genetic stock can be used to develop a range of new pigeonpea hybrids with high yield and adaptation. [ABSTRACT FROM AUTHOR]

Abstract: In Brassica oleracea, production of F1 hybrid seeds mainly makes use of the improved Ogura cytoplasmic male sterile (CMS) line. However, reliance on one particular line is a risk, and it would be advantageous to develop other CMS lines. In this study, we transferred Diplotaxis erucoides cytoplasm to B. oleracea cultivars using an alloplasmic B. rapaCMS line as a bridge plant to avoid incompatibility between donor and recipient plants. The new B. oleraceaCMS lines, which were derived by four generations of backcrossing, had small rudimentary anthers with no pollen grain and showed complete male sterility. There was no functional defect in other floral organs, and the ability to receive normal pollen did not appear to be impaired. Moreover, the B. oleraceaCMS lines carrying D. erucoides cytoplasm had larger leaf areas and a normal plastochron. As a consequence, the B. oleraceaCMS lines carrying D. erucoides cytoplasm have the potential to be valuable alternatives for use in commercial B. oleracea hybrid seed production. [ABSTRACT FROM AUTHOR]

In sexual organisms, division of the zygote initiates a new life cycle. Although several genes involved in zygote division are known in plants, how the zygote is activated to start embryogenesis has remained elusive. Here, we showed that a mutation in ZYGOTE-ARREST 3 (ZYG3) in Arabidopsis led to a tight zygote-lethal phenotype. Map-based cloning revealed that ZYG3 encodes the transfer RNA (tRNA) ligase AtRNL, which is a single-copy gene in the Arabidopsis genome. Expression analyses showed that AtRNL is expressed throughout zygotic embryogenesis, and in meristematic tissues. Using pAtRNL::cAtRNL-sYFP-complemented zyg3/zyg3 plants, we showed that AtRNL is localized exclusively in the cytoplasm, suggesting that tRNA splicing occurs primarily in the cytoplasm. Analyses using partially rescued embryos showed that mutation in AtRNL compromised splicing of intron-containing tRNA. Mutations of two tRNA endonuclease genes, SEN1 and SEN2, also led to a zygote-lethal phenotype. These results together suggest that tRNA splicing is critical for initiating zygote division in Arabidopsis. [ABSTRACT FROM AUTHOR]

Grain size and shape are two crucial traits that influence grain yield and grain appearance in rice. Although several factors that affect grain size have been described in rice, the molecular mechanisms underlying the determination of grain size and shape are still elusive. In this study we report that WIDE AND THICK GRAIN 1 ( WTG1) functions as an important factor determining grain size and shape in rice. The wtg1-1 mutant exhibits wide, thick, short and heavy grains and also shows an increased number of grains per panicle. WTG1 determines grain size and shape mainly by influencing cell expansion. WTG1 encodes an otubain-like protease, which shares similarity with human OTUB1. Biochemical analyses indicate that WTG1 is a functional deubiquitinating enzyme, and the mutant protein (wtg1-1) loses this deubiquitinating activity. WTG1 is expressed in developing grains and panicles, and the GFP- WTG1 fusion protein is present in the nucleus and cytoplasm. Overexpression of WTG1 results in narrow, thin, long grains due to narrow and long cells, further supporting the role of WTG1 in determining grain size and shape. Thus, our findings identify the otubain-like protease WTG1 to be an important factor that determines grain size and shape, suggesting that WTG1 has the potential to improve grain size and shape in rice. [ABSTRACT FROM AUTHOR]

Plant defensins are small, basic, cysteine-rich peptides, belonging to the antimicrobial peptide superfamily, commonly found in the plant kingdom. In this study, we cloned and characterized a plant defensin gene from Jatropha curcas (JcDef). JcDef carried conserved receptor binding sites and a cysteine motif, and it was phylogenetically grouped together with defensin Ec-AMP-D2-like in Elaeis guineensis. JcDef is localized to cytoplasm and highly expressed in young tissues with fast metabolism such as cotyledons and stem apexes. Transgenic expression of JcDef in tobacco showed enhanced resistance against sheath blight disease caused by R. solani, indicating the antibacterial function. [ABSTRACT FROM AUTHOR]

Lack of variability in sorghum is the main reason for the stagnation in crop improvement including low heterosis. Studies on somaclonal mutations of sorghum have led to the development of a diverse axillary branched grain sorghum mutant, Sb ABM of postrainy season variety A-1 (Annigeri-1) which bears multiple panicles. Considering its developmental significance and phenotypic diversity, this mutant was subjected to detailed genetic analysis. To exploit its genetic potentiality, the mutant was involved in a full diallel study along with ruling varieties to assess the combining ability and to quantify the magnitude of heterosis. Sb ABM performed exceptionally well in hybrid combinations for all the traits. Mean squares due to genotypes were highly significant for all the traits. The results on general combining ability revealed that Sb ABM was significantly better general combiner for all the traits studied. Majority of the hybrids involving Sb ABM as parental line exhibited high degree of heterosis for most of the traits, finally contributing to overall plant's vigour. However, Sb ABM did not restore fertility on both milo and maldandi cytoplasm. [ABSTRACT FROM AUTHOR]

We characterized the function of the rice cytosolic hexokinase OsHXK7 ( Oryza sativa He xo kinase 7), which is highly upregulated when seeds germinate under O2-deficient conditions. According to transient expression assays that used the promoter:luciferase fusion construct, OsHXK7 enhanced the glucose (Glc)-dependent repression of a rice α-amylase gene ( RAmy3D) in the mesophyll protoplasts of maize, but its catalytically inactive mutant alleles did not. Consistently, the expression of OsHXK7, but not its catalytically inactive alleles, complemented the Arabidopsis glucose insensitive2-1 ( gin2-1) mutant, thereby resulting in the wild type characteristics of Glc-dependent repression, seedling development, and plant growth. Interestingly, OsHXK7-mediated Glc-dependent repression was abolished in the O2-deficient mesophyll protoplasts of maize. This result provides compelling evidence that OsHXK7 functions in sugar signaling via a glycolysis-dependent manner under normal conditions, but its signaling role is suppressed when O2 is deficient. The germination of two null OsHXK7 mutants, oshxk7-1 and oshxk7-2, was affected by O2 deficiency, but overexpression enhanced germination in rice. This result suggests the distinct role that OsHXK7 plays in sugar metabolism and efficient germination by enforcing glycolysis-mediated fermentation in O2-deficient rice. [ABSTRACT FROM AUTHOR]

Mixed-linkage glucan ( MLG) is a significant cell wall carbohydrate in grasses and an important carbon source for human consumption and biofuel production. MLG biosynthesis depends on the biochemical activity of membrane spanning glucan synthases encoded by the CSLH and CSLF cellulose synthase-like gene families. CSLF proteins are the best characterized to date but relatively little information is known about their topology with respect to the biosynthetic membranes. In this study, we report on the topology of CSLF6 protein derived from the model grass species Brachypodium distachyon (Bd CSLF6) when it is expressed in heterologous systems. Using live cell imaging and immuno-electron microscopy analyses of tobacco epidermal cells expressing Bd CSLF6, we demonstrate that a functional yellow fluorescent protein ( YFP) fusion of Bd CSLF6 is localized to the Golgi apparatus and that the Golgi localization of Bd CSLF6 is sufficient for MLG biosynthesis. By implementing protease protection assays of Bd CSLF6 expressed in the yeast Pichia pastoris, we also demonstrate that the catalytic domain, the N-terminus and the C- terminus of the protein are exposed in the cytosol. Furthermore, we found that Bd CSLF6 is capable of producing MLG not only in tobacco cells but also in Pichia, which generally does not produce MLG. Together, these results support the conclusion that Bd CSLF6 can produce both of the linkages present in the (1,3;1,4)-β- d-glucan chain of MLG and that the product is channelled at the Golgi into the secretory pathway for deposition into the cell wall. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Yang et al., 214: 361–375. [ABSTRACT FROM AUTHOR]

Wood biomass is mainly made of secondary cell walls, whose formation is controlled by a multilevel network. The tandem CCCH zinc finger ( TZF) proteins involved in plant secondary wall formation are poorly understood., Two TZF genes, Pd C3 H17 and Pd C3 H18, were isolated from Populus deltoides and functionally characterized in Escherichia coli, tobacco, Arabidopsis and poplar., Pd C3 H17 and Pd C3 H18 are predominantly expressed in cells of developing wood, and the proteins they encode are targeted to cytoplasmic foci. Transcriptional activation assays showed that Pd MYB2/3/20/21 individually activated the Pd C3 H17 and Pd C3 H18 promoters, but Pd MYB3/21 were most significant. Electrophoretic mobility shift assays revealed that Pd MYB3/21 bound directly to the Pd C3 H17/18 promoters. Overexpression of Pd C3 H17/ 18 in poplar increased secondary xylem width and secondary wall thickening in stems, whereas dominant repressors of them had the opposite effects on these traits. Similar alteration in secondary wall thickening was observed in their transgenic Arabidopsis plants. q RT- PCR results showed that Pd C3 H17/ 18 regulated the expression of cellulose, xylan and lignin biosynthetic genes, and several wood-associated MYB genes., These results demonstrate that Pd C3 H17 and Pd C3 H18 are the targets of Pd MYB3 and Pd MYB21 and are an additional two components in the regulatory network of secondary xylem formation in poplar. [ABSTRACT FROM AUTHOR]

Recognition of microbe-associated molecular patterns ( MAMPs) initiates pattern-triggered immunity in host plants. Pattern recognition receptors ( PRRs) and receptor-like cytoplasmic kinases ( RLCKs) are the major components required for sensing and transduction of these molecular patterns. However, the regulation of RLCKs by PRRs and their specificity remain obscure. In this study we show that PBL27, an Arabidopsis ortholog of Os RLCK185, is an immediate downstream component of the chitin receptor CERK1 and contributes to the regulation of chitin-induced immunity in Arabidopsis. Knockout of PBL27 resulted in the suppression of several chitin-induced defense responses, including the activation of MPK3/6 and callose deposition as well as in disease resistance against fungal and bacterial infections. On the other hand, the contribution of PBL27 to flg22 signaling appears to be very limited, suggesting that PBL27 selectively regulates defense signaling downstream of specific PRR complexes. In vitro phosphorylation experiments showed that CERK1 preferentially phosphorylated PBL27 in comparison to BIK1, whereas phosphorylation of PBL27 by BAK1 was very low compared with that of BIK1. Thus, the substrate specificity of the signaling receptor-like kinases, CERK1 and BAK1, may determine the preference of downstream RLCKs. [ABSTRACT FROM AUTHOR]

* Premise of the study: Brassica juncea is a major source of edible oil in the Indian subcontinent and northern China. It is also used as a root and leaf vegetable in China and as a condiment in Europe and America. There is a long-standing view that B. juncea originated from multiple hybridization events between B. rapa and B. nigra and that hybridizations were always unidirectional with B. rapa as the cytoplasmic donor. These conclusions were, however, centered primarily on nuclear markers. * Methods: Two hundred forty-six accessions of B. juncea, B. rapa, and B. nigra were genotyped using chloroplast and nuclear simple sequence repeat (SSR) markers. * Key results: A structure analysis assigned B. juncea germplasm (122) into three major groups based on plasmotype variation. The bulk of Indian B. juncea genotypes were grouped along with Chinese and Australian accessions. This plasmotype was absent in sampled accessions of B. rapa (97), B. nigra (27), and other wild crucifers (10). The second group of B. juncea included East European genotypes and four accessions from India. It showed unambiguous homology with the predominant B. nigra plasmotype. The neighbor joining tree produced seven subgroups, arranged into two broad lineages. The first lineage included Indian, Australian, and Chinese B. juncea genotypes; it was associated with wild species belonging to the "rapa" lineage. Nuclear SSR marker-based analyses were largely supportive of results from chloroplast SSR analyses. * Conclusions: Based on these results, we provide the first report that B. juncea originated several times with both B. rapa and B. nigra as cytoplasmic donors in separate hybridization events. [ABSTRACT FROM AUTHOR]

Although heat-shock transcription factors are well characterized in the heat stress-related pathway, they are poorly understood in other stress responses. Here, we functionally characterized AtHsfA6a in the presence of exogenous abscisic acid ( ABA) and under high salinity and dehydration conditions. AtHsfA6a expression under normal conditions is very low, but was highly induced by exogenous ABA, NaCl and drought. Unexpectedly, the levels of AtHsfA6a transcript were not significantly altered under heat and cold stresses. Electrophoretic mobility shift assays and transient transactivation assays indicated that AtHsfA6a is transcriptionally regulated by ABA-responsive element binding factor/ ABA-responsive element binding protein, which are key regulators of the ABA signalling pathway. Additionally, fractionation and protoplast transient assays showed that AtHsfA6a was in cytoplasm and nucleus simultaneously; however, under conditions of high salinity the majority of AtHsfA6A was in the nucleus. Furthermore, at both seed germination and seedlings stage, plants overexpressing AtHsfA6a were hypersensitive to ABA and exhibited enhanced tolerance against salt and drought stresses. Finally, the microarray and qRT- PCR analyses revealed that many stress-responsive genes were up-regulated in the plants overexpressing AtHsfA6a. Taken together, the data strongly suggest that AtHsfA6a acts as a transcriptional activator of stress-responsive genes via the ABA-dependent signalling pathway. [ABSTRACT FROM AUTHOR]

Non-pungent bell pepper ( Capsicum annuum L.) lacks the cytoplasmic male sterility ( CMS) nuclear restorer allele, Rf, and CMS cannot be employed in its F1 hybrid seed production. To demonstrate that the genic male sterility ( GMS) system in non-pungent bell pepper can be converted to the CMS male sterility system, the conversion of GMS to CMS for non-pungent bell pepper line GC3 was conducted by introgression of S-type cytoplasm and the Rf allele from tropical pungent donors. After morphological traits were evaluated, two lines from BC1F1 containing S-type cytoplasm and four lines from BC2F2 containing Rf allele, phenotypically similar to GC3, were obtained and could be employed as CMS male sterile lines and restorer lines for non-pungent bell pepper. Four molecular markers potentially linked to traits of interest were also evaluated in BC1F1 and BC1F2 populations. This is the first time that GMS has been successfully converted to CMS in bell pepper, a significant contribution for bell pepper hybrid seed production. [ABSTRACT FROM AUTHOR]

Sunflower ( Helianthus annuus L.) productions reliance on a single source of cytoplasmic male sterility, PET1, derived from H. petiolaris Nutt., makes the crop genetically vulnerable. Twenty diverse cytoplasmic substitution lines from annual and perennial wild species were compared with the inbred line HA89 over four environments. Pairwise comparisons of alloplasmic male fertile ( MF) with euplasmic MF lines suggested that cytoplasm of perennial H. angustifolius increased lodging while perennial cytoplasms of H. mollis, H. grosseserratus, and H. divaricatus reduced head size and consequently reduced yield and will need to be used with caution. Lines having annual species, cytoplasms had no effects on agronomic traits. Comparisons of CMS HA 89 with 10 CMS lines suggested yield-reducing cytoplasmic effects of perennial H. maximiliani and annual H. annuus PI 413178 and PI 413024. Cytoplasmic effects on oil percentage and fatty acid composition were minimal and should not be of concern for sunflower breeders. In general, most cytoplasms of wild annual Helianthus species accommodate cultivated nuclear genes without drastic adverse interactions, and are potential sources of cytoplasmic diversity for sunflower breeding. [ABSTRACT FROM AUTHOR]

To assess the effect of alien cytoplasm and fertility restorer genes on agronomic and physiological traits in Brassica juncea, cytoplasmic male sterile ( CMS) and fertility restorer lines involving five alloplasms in three nuclear backgrounds were constituted through repeated backcrossing. These lines were evaluated along with euplasmic lines for agronomic traits in field experiments. Respiration efficiency of in vitro cultured hypocotyls, and chlorophyll content in leaves were also estimated. Significant adverse effects of trachystoma and catholica cytoplasms on yield-contributing traits and yield were noticed. The restorer gene corrected the floral defects in CMS trachystoma and restored yield to the level of euplasmic line, while it did so only partly in CMS catholica. Restorer genes had no adverse effect on traits in any of the systems. On the contrary, the Rf gene of moricandia CMS system exerted a positive effect on leaf chlorophyll content. Likewise, in vitro assay indicated the moricandia CMS system as vigorous. The moricandia CMS plants gave higher seed yield perhaps due to overall better vigour and higher leaf chlorophyll content. [ABSTRACT FROM AUTHOR]

Oxidative stress caused by ozone ( O3) affects plant development, but the roles of specific redox-homeostatic enzymes in O3 responses are still unclear. While growth day length may affect oxidative stress outcomes, the potential influence of day length context on equal-time exposures to O3 is not known. In Arabidopsis Col-0, day length affected the outcome of O3 exposure. In short-days ( SD), few lesions were elicited by treatments that caused extensive lesions in long days ( LD). Lesion formation was not associated with significant perturbation of glutathione, ascorbate, NADP( H) or NAD( H). To investigate roles of two genes potentially underpinning this redox stability, O3 responses of mutants for cytosolic NADP-isocitrate dehydrogenase ( icdh) and glutathione reductase 1 ( gr1) were analysed. Loss of ICDH function did not affect O3-induced lesions, but slightly increased glutathione oxidation, induction of other cytosolic NADPH-producing enzymes and pathogenesis-related gene 1 ( PR1). In gr1, O3-triggered lesions, salicylic acid accumulation, and induction of PR1 were all decreased relative to Col-0 despite enhanced accumulation of glutathione. Thus, even at identical irradiance and equal-time exposures, day length strongly influences phenotypes triggered by oxidants of atmospheric origin, while in addition to its antioxidant function, the GR-glutathione system seems to play novel signalling roles during O3 exposure. [ABSTRACT FROM AUTHOR]

Upland cotton ( Gossypium hirsutum L.) shows strong heterosis. However, heterosis is not widely utilized owing to the high cost of hybrid seed production. Creation of a photoperiod-sensitive genetic male sterile line could substantially reduce the cost of hybrid seed production in upland cotton. Such a mutant with virescent marker was found by space mutation in near-earth orbit and its traits had been stable after 4 years of selection in Anyang and Sanya, China. This mutant was fertile with an 11-12.5 h photoperiod when the temperature was higher than 21.5 °C and was sterile with a 13-14.5 h photoperiod. Genetic analysis indicated that both traits were controlled by a single recessive gene or two closely linked genes. Also, the cytological observations and transcriptome profiling analysis showed that the degradation of pollen grain cytoplasm should be the primary reason why the mutant line were male sterile under long-day conditions. [ABSTRACT FROM AUTHOR]

Programmed cell death ( PCD) in plants plays a key role in defense response and is promoted by the release of compartmentalized proteases to the cytoplasm. Yet the exact identity and control of these proteases is poorly understood. Serpins are an important group of proteins that uniquely curb the activity of proteases by irreversible inhibition; however, their role in plants remains obscure. Here we show that during cell death the Arabidopsis serpin protease inhibitor, At Serpin1, exhibits a pro-survival function by inhibiting its target pro-death protease, RD21. At Serpin1 accumulates in the cytoplasm and RD21 accumulates in the vacuole and in endoplasmic reticulum bodies. Elicitors of cell death, including the salicylic acid agonist benzothiadiazole and the fungal toxin oxalic acid, stimulated changes in vacuole permeability as measured by the changes in the distribution of marker dye. Concomitantly, a covalent At Serpin1- RD21 complex was detected indicative of a change in protease compartmentalization. Furthermore, mutant plants lacking RD21 or plants with At Serpin1 over-expression exhibited significantly less elicitor-stimulated PCD than plants lacking At Serpin1. The necrotrophic fungi Botrytis cinerea and Sclerotina sclerotiorum secrete oxalic acid as a toxin that stimulates cell death. Consistent with a pro-death function for RD21 protease, the growth of these necrotrophs was compromised in plants lacking RD21 but accelerated in plants lacking At Serpin1. The results indicate that AtSerpin1 controls the pro-death function of compartmentalized protease RD21 by determining a set-point for its activity and limiting the damage induced during cell death. [ABSTRACT FROM AUTHOR]

Nonsense-mediated mRNA decay (NMD) is a eukaryotic quality control system that identifies and degrades mRNAs containing premature termination codons (PTCs). If translation terminates at a PTC, the UPF1 NMD factor binds the terminating ribosome and recruits UPF2 and UPF3 to form a functional NMD complex, which triggers the rapid decay of the PTC-containing transcript. Although NMD deficiency is seedling lethal in plants, the mechanism of plant NMD remains poorly understood. To understand how the formation of the NMD complex leads to transcript decay we functionally mapped the UPF1 and SMG7 plant NMD factors, the putative key players of NMD target degradation. Our data indicate that the cysteine-histidine-rich (CH) and helicase domains of UPF1 are only essential for the early steps of NMD, whereas the heavily phosphory-lated N- and C-terminal regions play a redundant but essential role in the target transcript degradation steps of NMD. We also show that both the N- and the C-terminal regions of SMG7 are essential for NMD. The N terminus contains a phosphoserine-binding domain that is required for the early steps of NMD, whereas the C terminus is required to trigger the degradation of NMD target transcripts. Moreover, SMG7 is a P-body component that can also remobilize UPF1 from the cytoplasm into processing bodies (P bodies). We propose that the N- and C-terminal phosphorylated regions of UPF1 recruit SMG7 to the functional NMD complex, and then SMG7 transports the PTC-containing transcripts into P bodies for degradation. [ABSTRACT FROM AUTHOR]