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Aluminum toxicity is the main factor limiting the elongation of plant roots in acidic soil. The tree species Eucalyptus camaldulensis is considerably more resistant to aluminum than herbaceous model plants and crops. Hydrolyzable tannins (HTs) accumulating in E. camaldulensis roots can bind and detoxify the aluminum taken up by the roots. However, in herbaceous model plants, HTs do not accumulate and the genes involved in the HT biosynthetic pathway are largely unknown. The aim of this study was to establish a method for reconstituting the HT biosynthetic pathway in the HT non-accumulating model plant Nicotiana benthamiana. Four E. camaldulensis enzymes were transiently expressed in N. benthamiana leaves via Agrobacterium tumefaciens-mediated transformation. These enzymes included dehydroquinate dehydratase/shikimate dehydrogenases (EcDQD/SDH2 and EcDQD/SDH3), which catalyze the synthesis of gallic acid, the first intermediate of the HT biosynthetic pathway that branches off from the shikimate pathway. The others were UDP-glycosyltransferases (UGT84A25 and UGT84A26), which catalyze the conversion of gallic acid to β-glucogallin, the second intermediate. The co-expression of the EcDQD/SDHs in transgenic N. benthamiana leaf regions promoted the synthesis of gallic acid. Moreover, the co-expression of the UGT84As in addition to the EcDQD/SDHs resulted in the biosynthesis of β-glucogallin, the universal metabolic precursor of HTs. Thus, we successfully reconstituted a portion of the HT biosynthetic pathway in HT non-accumulating N. benthamiana plants. This heterologous gene expression system will be useful for co-expressing candidate genes involved in downstream reactions in the HT biosynthetic pathway and for clarifying their in planta functions. [ABSTRACT FROM AUTHOR]

Background: Natural rubber (cis-1,4-polyioprene, NR) is an indispensable industrial raw material obtained from the Pará rubber tree (H. brasiliensis). Natural rubber cannot be replaced by synthetic rubber compounds because of the superior resilience, elasticity, abrasion resistance, efficient heat dispersion, and impact resistance of NR. In NR production, latex is harvested by periodical tapping of the trunk bark. Ethylene enhances and prolongs latex flow and latex regeneration. Ethephon, which is an ethylene-releasing compound, applied to the trunk before tapping usually results in a 1.5- to 2-fold increase in latex yield. However, intense mechanical damage to bark tissues by excessive tapping and/or over-stimulation with ethephon induces severe oxidative stress in laticifer cells, which often causes tapping panel dryness (TPD) syndrome. To enhance NR production without causing TPD, an improved understanding of the molecular mechanism of the ethylene response in the Pará rubber tree is required. Therefore, we investigated gene expression in response to ethephon treatment using Pará rubber tree seedlings as a model system. Results: After ethephon treatment, 3270 genes showed significant differences in expression compared with the mock treatment. Genes associated with carotenoids, flavonoids, and abscisic acid biosynthesis were significantly upregulated by ethephon treatment, which might contribute to an increase in latex flow. Genes associated with secondary cell wall formation were downregulated, which might be because of the reduced sugar supply. Given that sucrose is an important molecule for NR production, a trade-off may arise between NR production and cell wall formation for plant growth and for wound healing at the tapping panel. Conclusions: Dynamic changes in gene expression occur specifically in response to ethephon treatment. Certain genes identified may potentially contribute to latex production or TPD suppression. These data provide valuable information to understand the mechanism of ethylene stimulation, and will contribute to improved management practices and/or molecular breeding to attain higher yields of latex from Pará rubber trees. [ABSTRACT FROM AUTHOR]

We have previously found that a transcription factor, ANAC046, acts as a positive regulator of chlorophyll degradation and senescence in Arabidopsis leaves. In this study, we introduced overexpression (OX) or dominant negative (SRDX) constructs into petunia ( Petunia hybrida) with a focus on the effect of the introduced gene on the flowers. The corolla limbs of the OX plants showed enhanced levels of chlorophyll catabolic genes resulting in lower chlorophyll content than those of wild-type plants. In the SRDX plants, chlorophyll catabolic genes were down-regulated and a higher level of chlorophyll was accumulated in the corolla limbs. There was no significant difference in the expression levels of senescence-associated genes and flower longevity between wild-type and transgenic plants. In petunia leaves, ANAC046 promoted chlorophyll degradation and senescence as previously observed in Arabidopsis leaves. We conclude that common or closely related transcription factors that regulate chlorophyll degradation may exist in the leaves and flowers, whereas those involved in senescence are different between them. [ABSTRACT FROM AUTHOR]

CRISPR/Cas9-based genome editing represents an unprecedented potential for plant breeding. Unlike animal cells, plant cells contain a rigid cell wall, genome editing tool delivery into plant cells is thus challenging. In particular, the delivery of the Cas9-gRNA ribonucleoprotein (RNP) into plant cells is desired since the transgene insertion into the genome should be avoided for industrial applications in plants. In this study, we present a novel RNP delivery approach in rice. We applied the sonication-assisted whisker method, conventionally developed for DNA delivery in plants, for RNP delivery in rice. Combined with marker gene delivery, we successfully isolated OsLCYβ genome-edited lines generated by RNPs. The calli and regenerated shoot of the OsLCYβ mutant showed abnormal carotenoid accumulation. In addition, we also detected, although at a low frequency, genome editing events in rice calli cells by RNP delivery using the sonication-assisted whisker method without any additional. Therefore, the sonication-assisted whisker method could be an attractive way to create RNP-based genome-edited lines in plants. [ABSTRACT FROM AUTHOR]

The secondary cell wall constitutes a rigid frame of cells in plant tissues where rigidity is required. Deposition of the secondary cell wall in fiber cells contributes to the production of wood in woody plants. The secondary cell wall is assembled through co-operative activities of many enzymes, and their gene expression is precisely regulated by a pyramidal cascade of transcription factors. Deposition of a transmuted secondary cell wall in empty fiber cells by expressing selected gene(s) in this cascade has not been attempted previously. In this proof-of-concept study, we expressed chimeric activators of 24 transcription factors that are preferentially expressed in the stem, in empty fiber cells of the Arabidopsis nst1-1 nst3-1 double mutant, which lacks a secondary cell wall in fiber cells, under the control of the NST3 promoter. The chimeric activators of MYB46, SND2 and ANAC075, as well as NST3, reconstituted a secondary cell wall with different characteristics from those of the wild type in terms of its composition. The transgenic lines expressing the SND2 or ANAC075 chimeric activator showed increased glucose and xylose, and lower lignin content, whereas the transgenic line expressing the MYB46 chimeric activator showed increased mannose content. The expression profile of downstream genes in each transgenic line was also different from that of the wild type. This study proposed a new screening strategy to identify factors of secondary wall formation and also suggested the potential of the artificially reconstituted secondary cell walls as a novel raw material for production of bioethanol and other chemicals. [ABSTRACT FROM AUTHOR]

Jasmonates (JAs) are plant hormones that regulate the balance between plant growth and responses to biotic and abiotic stresses. Although recent studies have uncovered the mechanisms for JA -induced responses in Arabidopsis thaliana , the mechanisms by which plants attenuate the JA -induced responses remain elusive. Here, we report that a basic helix-loop-helix–type transcription factor, ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR/JA-ASSOCIATED MYC2-LIKE1 (JAM1), acts as a transcriptional repressor and negatively regulates JA signaling. Gain-of-function transgenic plants expressing the chimeric repressor for JAM1 exhibited substantial reduction of JA responses, including JA -induced inhibition of root growth, accumulation of anthocyanin, and male fertility. These plants were also compromised in resistance to attack by the insect herbivore Spodoptera exigua. Conversely, jam1 loss-of-function mutants showed enhanced JA responsiveness, including increased resistance to insect attack. JAM1 and MYC2 competitively bind to the target sequence of MYC2, which likely provides the mechanism for negative regulation of JA signaling and suppression of MYC2 functions by JAM1. These results indicate that JAM1 negatively regulates JA signaling, thereby playing a pivotal role in fine-tuning of JA -mediated stress responses and plant growth. [ABSTRACT FROM AUTHOR]

Many eukaryotes have from one to three heat shock factors (Hsfs), but plants have more than 20 Hsfs, designated class A, B, and C. Class A Hsfs are activators of transcription, but details of the roles of individual Hsfs have not been fully characterized. We show here that Arabidopsis (Arabidopsis thaliana) HsfB1 and HsfB2b, members of class B, are transcriptional repressors and negatively regulate the expression of heat-inducible Hsfs (HsfA2, HsfA7a, HsfB1, and HsfB2b) and several heat shock pro genes. In hsfb1 hsfb2b double mutant plants, the expression of a large number of heat-inducible genes was enhanced in the non-heat condition (23°C) and the plants exhibited slightly higher heat tolerance at 42°C than the wild type, similar to Pro35S:HsfA plants. In addition, under extended heat stress conditions, expression of the heat-inducible Hsf genes remained consistent higher in hsfb1 hsfb2b than in the wild type. These data indicate that HsfB1 and HsfB2b suppress the general heat shoc response under non-heat-stress conditions and in the attenuating period. On the other hand, HsfB1 and HsfB2b appear to be necessary for the expression of heat stress-inducible heat shock protein genes under heat stress conditions, which is necessary for acquired thermotolerance. We show that the heat stress response is finely regulated by activation and repression activities of Hsfs in Arabidopsis. [ABSTRACT FROM AUTHOR]

The Arabidopsis thaliana NAC domain transcription factor, VASCULAR-RELATED NAC-DOMAIN7 (VND7), acts as a key regulator of xylem vessel differentiation. In order to identify direct target genes of VND7, we performed global transcriptome analysis using Arabidopsis transgenic lines in which VND7 activity could be induced post-translationally. This analysis identified 63 putative direct target genes of VND7, which encode a broad range of proteins, such as transcription factors, IRREGULAR XYLEM proteins and proteolytic enzymes, known to be closely associated with xylem vessel formation. Recombinant VND7 protein binds to several promoter sequences present in candidate direct target genes: specifically, in the promoter of XYLEM CYSTEINE PEPTIDASE1, two distinct regions were demonstrated to be responsible for VND7 binding. We also found that expression of VND7 restores secondary cell wall formation in the fiber cells of inflorescence stems of nst1 nst3 double mutants, as well as expression of NAC SECONDARY WALL THICKENING PROMOTING FACTOR3 ( NST3, however, the vessel-type secondary wall deposition was observed only as a result of VND7 expression. These findings indicated that VND7 upregulates, directly and/or indirectly, many genes involved in a wide range of processes in xylem vessel differentiation, and that its target genes are partially different from those of NSTs. [ABSTRACT FROM AUTHOR]

Summary: Many multicellular organisms have remarkable capability to regenerate new organs after wounding. As a first step of organ regeneration, adult somatic cells often dedifferentiate to reacquire cell proliferation potential, but mechanisms underlying this process remain unknown in plants. Here we show that an AP2/ERF transcription factor, WOUND INDUCED DEDIFFERENTIATION 1 (WIND1), is involved in the control of cell dedifferentiation in Arabidopsis. WIND1 is rapidly induced at the wound site, and it promotes cell dedifferentiation and subsequent cell proliferation to form a mass of pluripotent cells termed callus. We further demonstrate that ectopic overexpression of WIND1 is sufficient to establish and maintain the dedifferentiated status of somatic cells without exogenous auxin and cytokinin, two plant hormones that are normally required for cell dedifferentiation []. In vivo imaging of a synthetic cytokinin reporter [] reveals that wounding upregulates the B-type ARABIDOPSIS RESPONSE REGULATOR (ARR)-mediated cytokinin response and that WIND1 acts via the ARR-dependent signaling pathway to promote cell dedifferentiation. This study provides novel molecular insights into how plants control cell dedifferentiation in response to wounding. [ABSTRACT FROM AUTHOR]

Yeast one-hybrid screening is widely used for the identification of transcription factors (TFs) that interact with specific DNA sequences. However, screening a whole cDNA library is not efficient for the identification of TFs because TF genes represent only a small percentage of clones in a cDNA library. Here, we present the development of an efficient yeast one-hybrid screening system using a prey library composed only of approximately 1,500 TF cDNAs of Arabidopsis thaliana. This library enabled us to isolate a TF that binds to a specific promoter sequence with high efficiency, even when the promoter region of the gene of interest was directly employed as bait. Furthermore, this library was also successfully applied as a yeast two-hybrid library to find TFs that interact with specific proteins. This efficient system will contribute to the elucidation of gene regulatory networks in plants. [ABSTRACT FROM AUTHOR]

Coordination of the maintenance of the undifferentiated fate of cells in the shoot meristem and the promotion of cellular differentiation in plant organs is essential for the development of plant shoots. CINCINNATA-like (CIN-like) TEOSINTE BRANCHED1, CYCLOIDEA, and PCF (TCP) transcription factors are involved in this coordination via the negative regulation of CUP-SHAPED COTYLEDON (CUC) genes, which regulate the formation of shoot meristems and the specification of organ boundaries. However, the molecular mechanism of the action of CIN-like TCPs is poorly understood. We show here that TCP3, a model of CIN-like TCPs of Arabidopsis thaliana , directly activates the expression of genes for miR164, ASYMMETRIC LEAVES1 (AS1), INDOLE-3-ACETIC ACID3/SHORT HYPOCOTYL2 (IAA3/SHY2), and SMALL AUXIN UP RNA (SAUR) proteins. Gain of function of these genes suppressed the formation of shoot meristems and resulted in the fusion of cotyledons, whereas their loss of function induced ectopic expression of CUC genes in leaves. Our results indicate that miR164, AS1 , IAA3/SHY2 , and SAUR partially but cooperatively suppress the expression of CUC genes. Since CIN -like TCP genes were revealed to act dose dependently in the differentiation of leaves, we propose that evolutionarily diverse CIN-like TCPs have important roles in the signaling pathways that generate different leaf forms, without having any lethal effects on shoots. [ABSTRACT FROM AUTHOR]

Most transcription factors act either as activators or repressors, and no such factors with dual function have been unequivocally identified and characterized in plants. We demonstrate here that the Arabidopsis thaliana protein WUSCHEL (WUS), which regulates the maintenance of stem cell populations in shoot meristems, is a bifunctional transcription factor that acts mainly as a repressor but becomes an activator when involved in the regulation of the AGAMOUS (AG) gene. We Show that the WUS box, which is conserved among WOX genes, is the domain that is essential for all the activities of WUS, namely, for regulation of stem cell identity and size of floral meristem. All the known activities of WUS were eliminated by mutation of the WUS box, including the ability of WUS to induce the expression of AG. The mutation of the WUS box was complemented by fusion of an exogenous repression domain, with resultant induction of somatic embryogenesis in roots and expansion of floral meristems as observed upon ectopic expression of WUS. By contrast, fusion of an exogenous activation domain did not result in expanded floral meristems but induced flowers similar to those induced by the ectopic expression of AG. Our results demonstrate that WUS acts mainly as a repressor and that its function changes from that of a repressor to that of an activator in the case of regulation of the expression of AG. [ABSTRACT FROM AUTHOR]

Three distinct pattern elements of the silique are thought to contribute to its dehiscence: a separation layer, cells with a secondary wall adjacent to the separation layer, and a valve endocarp layer with secondary wall. However, the role of the secondary wall has not been proven, and the factors that regulate its formation in siliques remain to be characterized. We show here that secondary wall formation in siliques is necessary for dehiscence, and that two plant-specific transcription factors, NAC SECONDARY WALL THICKENING PROMOTING FACTOR 1 and 3 (NST1 and NST3), regulate its formation in siliques of Arabidopsis. The promoters of the NST1 and NST3 genes were active in the valve endocarp layer and in cells surrounding vascular vessels in the replum, and NST1 promoter activity only was faintly detectable at valve margins. In nst1 mutants, specific loss of secondary walls was evident at valve margins, while nst1 nst3 double mutants lacked secondary walls in all parts of the siliques, with the exception of vascular vessels. These siliques were similarly indehiscent. The promoters of two tissue-identity genes, INDEHISCENT ( IND) and SHATTERPROOF2 ( SHP2), were as active in the nst1 nst3 mutant as in the wild-type. Moreover, the ectopic secondary wall formation that occurs in the fruitfull ( ful) mutant was absent in the ful nst1 double mutant. We propose that secondary walls in valve margins are required for dehiscence, and that NST1 and NST3 regulate their formation in siliques in a partially redundant manner after the establishment of tissue identity. [ABSTRACT FROM AUTHOR]

Seed morphogenesis consists of embryogenesis and the development of maternal tissues such as the inner and outer integuments, both of which give rise to seed coats. We show that expression of chimeric repressors derived from NAC-REGULATED SEED MORPHOLOGY1 and -2 (NARS1 and NARS2, also known as NAC2 and NAM, respectively) caused aberrant seed shapes in Arabidopsis thaliana. Double knockout mutant nars1 nars2 exhibited abnormally shaped seeds; moreover, neither nars1 nor nars2 produced abnormal seeds, indicating that NARS1 and NARS2 redundantly regulate seed morphogenesis. Degeneration of the integuments in nars1 nars2 was markedly delayed, while that of the wild type occurred around the torpedo-shaped embryo stage. Additionally, nars1 nars2 showed a defect in embryogenesis: some nars1 nars2 embryos were developmentally arrested at the torpedo-shaped embryo stage. Unexpectedly, however, neither NARS1 nor NARS2 was expressed in the embryo at this stage, although they were found to be expressed in the outer integument. Wild-type pistils pollinated with nars1 nars2 pollen generated normal seeds, while the reverse crossing generated abnormal seeds. Taken together, these results indicate that NARS1 and NARS2 regulate embryogenesis by regulating the development and degeneration of ovule integuments. Our findings suggest that there is an intertissue communication between the embryo and the maternal integument. [ABSTRACT FROM AUTHOR]

Wood is formed by the successive addition of secondary xylem, which consists of cells with a conspicuously thickened secondary wall composed mainly of lignin and cellulose. Several genes involved in lignin and cellulose biosynthesis have been characterized, but the factors that regulate the formation of secondary walls in woody tissues remain to be identified. In this study, we show that plant-specific transcription factors, designated NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1) and NST3, are key regulators of the formation of secondary walls in woody tissues of Arabidopsis thaliana. In nst1-1 nst3-1 double knockout plants, the secondary wall thickenings in interfascicular fibers and secondary xylem, except for vascular vessels, were completely suppressed without affecting formation of cells destined to be woody tissues. Conversely, as shown previously for NST1, overexpression of NST3 induced ectopic secondary wall thickenings in various aboveground tissues. Furthermore, the expression of chimeric repressors derived from NST1 and NST3 suppressed secondary wall thickenings in the presumptive interfascicular fibers. Because putative orthologs of NST1 and NST3 are present in the genome of poplar, our results suggest that they are also key regulators of the formation of secondary walls in woody plants and could be used as a tool for the genetic engineering of wood and its derivatives. [ABSTRACT FROM AUTHOR]

Male and female sterile plants are particularly useful for the effective production of commercial hybrid plants and for preventing the diffusion of seeds or pollen grains of genetically modified plants in the open field. In an attempt to create several types of sterile plant by genetic manipulation, we applied our Chimeric REpressor Gene- Silencing Technology (CRES-T) to four transcription factors, namely APETALA3, AGAMOUS, LEAFY and AtMYB26, involved in the regulation of petal and stamen identity, stamen and carpel identity, floral meristem identity and anther dehiscence, respectively, in Arabidopsis. Transgenic plants expressing each chimeric repressor exhibited, at high frequency, a sterile phenotype that resembled the loss-of-function phenotype of each corresponding gene. Furthermore, in the monocotyledonous crop plant ‘rice’, expression of the chimeric repressor derived from SUPERWOMAN1, the rice orthologue of APETALA3, resulted in the male sterile phenotype with high efficiency. Our results indicate that CRES-T provides a powerful tool for controlling the fertility of both monocots and dicots by exploiting transcription factors that are strongly conserved amongst plants. [ABSTRACT FROM AUTHOR]

In plants, secondary wall thickenings play important roles in various biological processes, although the factors regulating these processes remain to be characterized. We show that expression of chimeric repressors derived from NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1) and NST2 in Arabidopsis thaliana resulted in an anther dehiscence defect due to loss of secondary wall thickening in anther endothecium. Plants with double, but not single, T-DNA-tagged lines for NST1 and NST2 had the same anther-indehiscent phenotype as transgenic plants that expressed the individual chimeric repressors, indicating that NST1 and NST2 are redundant in regulating secondary wall thickening in anther walls. The activity of the NST2 promoter was particularly strong in anther tissue, while that of the NST1 promoter was detected in various tissues in which lignified secondary walls develop. Ectopic expression of NST1 or NST2 induced ectopic thickening of secondary walls in various aboveground tissues. Epidermal cells with ectopic thickening of secondary walls had structural features similar to those of tracheary elements. However, among genes involved in the differentiation of tracheary elements, only those related to secondary wall synthesis were clearly upregulated. None of the genes involved in programmed cell death were similarly affected. Our results suggest NAC transcription factors as possible regulators of secondary wall thickening in various tissues. [ABSTRACT FROM AUTHOR]

We reported previously that the carboxy-terminal 30 amino acids of SUPERMAN (SUPRD) function as a repression domain in Arabidopsis. In this study, we identified the peptide sequences in SUPRD that is both necessary and sufficient for repression of transcription. To our surprise, the hexapeptide DLELRL was sufficient, by itself, to confer the ability to repress transcription on a DNA-binding domain. A database search revealed that there are 32 TFIIIA-type zinc finger proteins in the Arabidopsis genome that contain a hexapeptide sequence similar or identical to that of DLELRL. These peptides acted as repression domains, suggesting that these zinc finger proteins might function as active repressors. Further mutational analysis within DLELRL revealed that an amphiphilic motif composed of six amino acids (XLxLXL) with preferences at the first and fifth positions is necessary and sufficient for strong repression. An assay of positional effects suggested that GAL4DB–DLELRL might function as a short-range repressor. A possible mechanism of the DLELRL-mediated repression is discussed. [Copyright &y& Elsevier]

A 38-bp pollen-specific cis-acting region of the AVP1 gene is involved in the expression of the Arabidopsis thaliana V-PPase during pollen development. Here, we report the isolation and structural characterization of AtVOZ1 and AtVOZ2, novel transcription factors that bind to the 38-bp cis-acting region of A. thaliana V-PPase gene, AVP1. AtVOZ1 and AtVOZ2 show 53% amino acid sequence similarity. Homologs of AtVOZ1 and AtVOZ2 are found in various vascular plants as well as a moss, Physcomitrella patens. Promoter-β-glucuronidase reporter analysis shows that AtVOZ1 is specifically expressed in the phloem tissue and AtVOZ2 is strongly expressed in the root. In vivo transient effector-reporter analysis in A. thaliana suspension-cultured cells demonstrates that AtVOZ1 and AtVOZ2 function as transcriptional activators in the Arabidopsis cell. Two conserved regions termed Domain-A and Domain-B were identified from an alignment of AtVOZ proteins and their homologs of O. sativa and P. patens. AtVOZ2 binds as a dimer to the specific palindromic sequence, GCGTNx7ACGC, with Domain-B, which is comprised of a functional novel zinc coordinating motif and a conserved basic region. Domain-B is shown to function as both the DNA-binding and the dimerization domains of AtVOZ2. From highly the conservative nature among all identified VOZ proteins, we conclude that Domain-B is responsible for the DNA binding and dimerization of all VOZ-family proteins and designate it as the VOZ-domain. [ABSTRACT FROM AUTHOR]

SUMMARY: Knotted1‐like homeodomain (KNOX) proteins are essential in regulating plant organ differentiation. Land plants, including tomato (Solanum lycopersicum), have two classes of the KNOX protein family, namely, class I (KNOX I) and class II KNOX (KNOX II). While tomato KNOX I proteins are known to stimulate chloroplast development in fruit, affecting fruit coloration, the role of KNOX II proteins in this context remains unclear. In this study, we employ CRISPR/Cas9 to generate knockout mutants of the KNOX II member, SlKN5. These mutants display increased leaf complexity, a phenotype commonly associated with reduced KNOX II activity, as well as enhanced accumulation of chloroplasts and chlorophylls in smaller cells within young, unripe fruit. RNA‐seq data analyses indicate that SlKN5 suppresses the transcriptions of genes involved in chloroplast biogenesis, chlorophyll biosynthesis, and gibberellin catabolism. Furthermore, protein–protein interaction assays reveal that SlKN5 physically interacts with three transcriptional repressors from the BLH1‐clade of BEL1‐like homeodomain (BLH) protein family, SlBLH4, SlBLH5, and SlBLH7, with SlBLH7 showing the strongest interaction. CRISPR/Cas9‐mediated knockout of these SlBLH genes confirmed their overlapping roles in suppressing chloroplast biogenesis, chlorophyll biosynthesis, and lycopene cyclization. Transient assays further demonstrate that the SlKN5–SlBLH7 interaction enhances binding capacity to regulatory regions of key chloroplast‐ and chlorophyll‐related genes, including SlAPRR2‐like1, SlCAB‐1C, and SlGUN4. Collectively, our findings elucidate that the KNOX II SlKN5‐SlBLH regulatory modules serve to inhibit fruit greening and subsequently promote lycopene accumulation, thereby fine‐tuning the color transition from immature green fruit to mature red fruit. Significance Statement: This study shed light on regulatory mechanisms of plastid development in fruits by demonstrating that the class II knotted‐like homeodomain protein SlKN5 negatively regulates chloroplast number and chlorophyll accumulation in tomato fruit development. SlKN5 interacts with BEL1‐like homeodomain protein SlBLH7 and its paralogs to suppress SlAPRR2‐like1 and chlorophyll biosynthetic genes, promoting the developmental shift from growth phase to onset of ripening. This highlights the crucial role of the SlKN5‐BLH module in the regulation of tomato fruit coloration. [ABSTRACT FROM AUTHOR]

Beneficial Bacillus subtilis (BS) symbiosis could combat root pathogenesis, but it relies on root‐secreted sugars. Understanding the molecular control of sugar flux during colonization would benefit biocontrol applications. The SWEET (Sugar Will Eventually Be Exported Transporter) uniporter regulates microbe‐induced sugar secretion from roots; thus, its homologs may modulate sugar distribution upon BS colonization. Quantitative polymerase chain reaction revealed that gene transcripts of SWEET2, but not SWEET16 and 17, were significantly induced in seedling roots after 12 h of BS inoculation. Particularly, SWEET2‐β‐glucuronidase fusion proteins accumulated in the apical mature zone where BS abundantly colonized. Yet, enhanced BS colonization in sweet2 mutant roots suggested a specific role for SWEET2 to constrain BS propagation, probably by limiting hexose secretion. By employing yeast one‐hybrid screening and ectopic expression in Arabidopsis protoplasts, the transcription factor AHL29 was identified to function as a repressor of SWEET2 expression through the AT‐hook motif. Repression occurred despite immunity signals. Additionally, enhanced SWEET2 expression and reduced colonies were specifically detected in roots of BS‐colonized ahl29 mutant. Taken together, we propose that BS colonization may activate repression of AHL29 on SWEET2 transcription that would be enhanced by immunity signals, thereby maintaining adequate sugar secretion for a beneficial Bacillus association. Summary statement: Arabidopsis vacuolar SWEET2 transporter limits root sugar secretion upon colonization with beneficial Bacillus subtilis. The AT‐hook protein AHL29 binds to the SWEET2 promoter to repress its immunity‐induced expression, thereby promoting adequate carbon for a mutualistic association with Bacillus. [ABSTRACT FROM AUTHOR]

To mitigate the effects of global warming and to preserve the limited fossil fuel resources, an increased exploitation of plant-based materials and fuels is required, which would be one of the most important innovations related to sustainable development. Cell walls account for the majority of plant dry biomass and so is the target of such innovations. In this review, we discuss recent advances in in planta cell wall engineering through genetic manipulations, with a focus on wild-type-based and mutant-based approaches. The long history of using a wild-type-based approach has resulted in the development of many strategies for manipulating lignin, hemicellulose and pectin to decrease cell wall recalcitrance. In addition to enzyme-encoding genes, many transcription factor genes important for changing relevant cell wall characteristics have been identified. Although mutant-based cell wall engineering is relatively new, it has become feasible due to the rapid development of genome-editing technologies and systems biology–related research; we will soon enter an age of designed artificial wood production via complex genetic manipulations of many industrially important trees and crops. [ABSTRACT FROM AUTHOR]

SUMMARY: Formation of secondary cell wall (SCW) is tightly regulated spatiotemporally by various developmental and environmental signals. Successful fine‐tuning of the trade‐off between SCW biosynthesis and stress responses requires a better understanding of how plant growth is regulated under environmental stress conditions. However, the current understanding of the interplay between environmental signaling and SCW formation is limited. The lipid‐derived plant hormone jasmonate (JA) and its derivatives are important signaling components involved in various physiological processes including plant growth, development, and abiotic/biotic stress responses. Recent studies suggest that JA is involved in SCW formation but the signaling pathway has not been studied for how JA regulates SCW formation. We tested this hypothesis using the transcription factor MYB46, a master switch for SCW biosynthesis, and JA treatments. Both the transcript and protein levels of MYB46, a master switch for SCW formation, were significantly increased by JA treatment, resulting in the upregulation of SCW biosynthesis. We then show that this JA‐induced upregulation of MYB46 is mediated by MYC2, a central regulator of JA signaling, which binds to the promoter of MYB46. We conclude that this MYC2‐MYB46 module is a key component of the plant response to JA in SCW formation. Significance Statement: Successful fine‐tuning of the trade‐off between secondary cell wall biosynthesis and stress responses requires a better understanding of how plant growth is regulated under environmental stress conditions. We show that the lipid‐derived plant hormone jasmonate, a critical player in environmental signaling, upregulates secondary cell wall formation. [ABSTRACT FROM AUTHOR]

Appropriate pectin deposition in cell walls is important for cell growth in plants. Rhamnogalacturonan II (RG-II) is a portion of pectic polysaccharides; its borate crosslinking is essential for maintenance of pectic networks. However, the overall process of RG-II synthesis is not fully understood. To identify a novel factor for RG-II deposition or dimerization in cell walls, we screened Arabidopsis mutants with altered boron (B)-dependent growth. The mutants exhibited alleviated disorders of primary root and stem elongation, and fertility under low B, but reduced primary root lengths under sufficient B conditions. Altered primary root elongation was associated with cell elongation changes caused by loss of function in AtTMN1 (Transmembrane Nine 1)/ EMP12 , which encodes a Golgi-localized membrane protein of unknown function that is conserved among eukaryotes. Mutant leaf and root dry weights were lower than those of wild-type plants, regardless of B conditions. In cell walls, AtTMN1 mutations reduced concentrations of B, RG-II specific 2-keto-3-deoxy monosaccharides, and rhamnose largely derived from rhamnogalacturonan I (RG-I), suggesting reduced RG-II and RG-I. Together, our findings demonstrate that AtTMN1 is required for the deposition of RG-II and RG-I for cell growth and suggest that pectin modulates plant growth under low B conditions. [ABSTRACT FROM AUTHOR]

• Lignocellulosic biomass utilization is crucial for sustainable development. • Lignin has two characteristics, a useful biomass component and an inhibitor of wall polysaccharides' enzymatic hydrolysis. • Microbial ligninolytic enzymes are valuable for biomass pretreatment. • Bacterial enzymes for converting lignin-derived aromatics are useful for lignin bioengineering. • The selective bacterial β–O–4-cleaving system is a potential novel biopretreatment tool Lignocellulosic biomass represents a crucial resource for achieving sustainable development by replacing petroleum-based production systems. Lignin, a major component of plant cell walls, has significant potential as a bioresource; however, it is an obstacle in lignocellulosic biomass utilization due to its recalcitrance. Consequently, decomposition or removal of lignin is a crucial step to utilize cell wall components. In nature, lignin may be degraded via two stages: depolymerization and the mineralization of the resulting heterogeneous low-molecular-weight aromatic species. Microbial enzymes responsible for the former could be attractive tools for lignin decomposition during biomass pretreatment, and enzymes involved in the latter are useful for lignin valorization through the production of value-added chemicals. Moreover, specific microbial enzymes could reduce the recalcitrance of lignocellulosic biomass via plant cell wall bioengineering. This review focuses on microbial enzymes that are responsible for lignin degradation and on their applications to biological lignocellulosics pretreatment and biotechnological lignin engineering. [ABSTRACT FROM AUTHOR]

Buckwheat ( Fagopyrum esculentum ) contains high amounts of flavonoids, especially flavonols (e.g., rutin), which are thought to be highly beneficial for human health. Little is known, however, about the regulation of flavonol synthesis in buckwheat. We identified a buckwheat gene encoding an R2R3 MYB transcription factor, and named this gene FeMYBF1 . Analysis of the deduced amino acid sequence and phylogenetic analysis suggested that FeMYBF1 encodes an ortholog of the Arabidopsis flavonol regulators AtMYB11, AtMYB12 and AtMYB111. Expression of FeMYBF1 in a flavonol-deficient Arabidopsis triple mutant ( myb11 myb12 myb111 ) restored flavonol synthesis. Constitutive expression of FeMYBF1 driven by the CaMV 35S promoter in Arabidopsis resulted in over-accumulation of flavonol glycosides and upregulation of the expression of AtFLS1 . Transient expression assays showed that FeMYBF1 activated the promoter of the Arabidopsis gene encoding AtFLS1, and the promoters of buckwheat genes related to anthocyanin and proanthocyanidin synthesis such as dihydroflavonol 4-reductase ( DFR ) and leucoanthocyanidin dioxygenase ( LDOX ) in addition to genes encoding FLS. The results indicate that FeMYBF1 regulates flavonol synthesis and may have a role in synthesis of other flavonoid compounds, and also that buckwheat may have alternative pathway of flavonol synthesis through DFR and LDOX. [ABSTRACT FROM AUTHOR]

An abstract of the conference paper "Vascular-related NAC-domain 7 directly regulates a broad range of genes for xylem vessel differentiation," by Nobutaka Mitsuda and colleagues is presented.

Endosperm–embryo development in flowering plants is regulated coordinately by signal exchange during seed development. However, such a reciprocal control mechanism has not been clearly identified. In this study, we identified an endosperm‐specific gene, LBD35, expressed in an embryonic development‐dependent manner, by a comparative transcriptome and cytological analyses of double‐fertilized and single‐fertilized seeds prepared by using the kokopelli mutant, which frequently induces single fertilization events. Transcriptome analysis using LBD35 as a marker of the central cell fertilization event identified that 141 genes, including 31 genes for small cysteine‐rich peptides, are expressed in a double fertilization‐dependent manner. Our results reveal possible embryonic signals that regulate endosperm gene expression and provide a practicable method to identify genes involved in the communication during endosperm–embryo development. [ABSTRACT FROM AUTHOR]

Apomixis, defined as the transfer of maternal germplasm to offspring without fertilization, enables the fixation of F1-useful traits, providing advantages in crop breeding. However, most apomictic plants require pollination to produce the endosperm. The endosperm is essential for embryogenesis, and its development is suppressed until fertilization. We show that the expression of a chimeric repressor of the Elongation of Siliques without Pollination 3 (ESP3) gene (Pro35S:ESP3-SRDX) induces ovule enlargement without fertilization in Arabidopsis thaliana. The ESP3 gene encodes a protein similar to the flowering Wageningen homeodomain transcription factor containing a StAR-related lipid transfer domain. However, ESP3 lacks the homeobox-encoding region. Genes related to the cell cycle and sugar metabolism were upregulated in unfertilized Pro35S:ESP3-SRDX ovules similar to those in fertilized seeds, while those related to autophagy were downregulated similar to those in fertilized seeds. Unfertilized Pro35S:ESP3-SRDX ovules partially nourished embryos when only the egg was fertilized, accumulating hexoses without central cell proliferation. ESP3 may regulate nutrient flow during seed development, and ESP3-SRDX could be a useful tool for complete apomixis that does not require pseudo-fertilization. [ABSTRACT FROM AUTHOR]

Cypridina noctiluca luciferase has been utilized for biochemical and molecular biological applications, including bioluminescent enzyme immunoassays, far-red luminescence imaging, and high-throughput reporter assays. Some of these applications require a large amount of purified luciferase. However, conventional protein expression systems are not capable of producing sufficient quantities of protein with a high quality and purity without laborious and costly purification processes. To improve the productivity and expand the breadth of possibilities for Cypridina luciferase applications, we employed a variety of secretion expression systems, including yeast, mammalian cells, and silk worms. In this study, we established a simple production procedure using plant cell cultures. The plant cell culture BY-2 efficiently secreted luciferase, which was easily purified using a simple one-step ion-exchange chromatography method. The production yield was 20–30 mg of luciferase per liter of culture medium, and its K m for the luciferin (0.45 μM) was similar to that of the native protein. Additionally, we characterized its glycosylation pattern and confirmed that the two potential N -glycosylation sites were modified with plant-type oligosaccharide chains. Interestingly, the oligosaccharide chains could be trimmed without any detectable decrease in recombinant protein activity. Therefore, the results of our study indicate that this method offers a more cost-effective production method for Cypridina luciferase than conventional methods. [ABSTRACT FROM AUTHOR]

Jasmonate (JA) is an important hormone involved in regulating diverse responses to environmental factors as well as growth and development, and its signalling is influenced by other hormones such as ethylene (ET). However, our understanding of the regulatory relationship between the JA and ET signalling pathways is limited. In this study, we isolated an Arabidopsis JA-hypersensitive mutant, jah3 (jasmonate hypersensitive3)- 1. Map-based cloning revealed that the JAH3 gene corresponds to At4g16535. JAH3 encodes a protein of unknown function whose amino acid sequence has similarity to leukocyte receptor cluster-like protein. The mutation in jah3-1 is caused by a single nucleotide change from A to T at position 220 of 759 bp. Using CRISPR-Cas9, we generated a second allele, jah3-2, that encodes a truncated protein. Both of these loss-of-function alleles resulted in hypersensitivity to JA, ET-induced root growth inhibition, and accelerated dark-induced senescence. Double mutant analyses employing coronatine insensitive 1 (coi1) and ethylene insensitive 3 (ein3) mutants (jah3 coi1 and jah3 ein3) demonstrated that the hypersensitive phenotypes of the jah3 mutants are mediated by JA and ET signalling components COI1 and EIN3. Therefore, we propose that JAH3 is a negative regulator of both JA and ET signalling. [ABSTRACT FROM AUTHOR]

SUMMARY: Arabidopsis possesses approximately 2000 transcription factors (TFs) in its genome. They play pivotal roles in various biological processes but analysis of their function has been hampered by the overlapping nature of their activities. To uncover clues to their function, we generated inducible TF lines using glucocorticoid receptor (GR) fusion techniques in Arabidopsis. These TF‐GR lines each express one of 1255 TFs as a fusion with the GR gene. An average 14 lines of T2 transgenic TF‐GR lines were generated for each TF to monitor their function. To evaluate these transcription lines, we induced the TF‐GR lines of phytochrome‐interacting factor 4, which controls photomorphogenesis, with synthetic glucocorticoid dexamethasone. These phytochrome‐interacting factor 4‐GR lines showed the phenotype described in a previous report. We performed screening of the other TF‐GR lines for TFs involved in light signaling under blue and far‐red light conditions and identified 13 novel TF candidates. Among these, we found two lines showing higher anthocyanin accumulation under light conditions and we examined the regulating genes. These results indicate that the TF‐GR lines can be used to dissect functionally redundant genes in plants and demonstrate that the TF‐GR line collection can be used as an effective tool for functional analysis of TFs. Significance Statement: We generated inducible transcription factor (TF) lines in Arabidopsis, TF‐glucocorticoid receptor (GR) lines, each expressing one of 1255 TFs as a fusion with the GR gene that affects transportation to the nucleus by application of an inducer, dexamethasone. After evaluating these lines by examination of phytochrome‐interacting factor 4, we performed screening for TFs involved in light signaling from the TF‐GR lines and analyzed two that showed higher anthocyanin accumulation under light conditions. [ABSTRACT FROM AUTHOR]

SUMMARY: Lignin is a phenolic polymer deposited in the plant cell wall, and is mainly polymerized from three canonical monomers (monolignols), i.e. p‐coumaryl, coniferyl and sinapyl alcohols. After polymerization, these alcohols form different lignin substructures. In dicotyledons, monolignols are biosynthesized from phenylalanine, an aromatic amino acid. Shikimate acts at two positions in the route to the lignin building blocks. It is part of the shikimate pathway that provides the precursor for the biosynthesis of phenylalanine, and is involved in the transesterification of p‐coumaroyl‐CoA to p‐coumaroyl shikimate, one of the key steps in the biosynthesis of coniferyl and sinapyl alcohols. The shikimate residue in p‐coumaroyl shikimate is released in later steps, and the resulting shikimate becomes available again for the biosynthesis of new p‐coumaroyl shikimate molecules. In this study, we inhibited cytosolic shikimate recycling in transgenic hybrid aspen by accelerated phosphorylation of shikimate in the cytosol through expression of a bacterial shikimate kinase (SK). This expression elicited an increase in p‐hydroxyphenyl units of lignin and, by contrast, a decrease in guaiacyl and syringyl units. Transgenic plants with high SK activity produced a lignin content comparable to that in wild‐type plants, and had an increased processability via enzymatic saccharification. Although expression of many genes was altered in the transgenic plants, elevated SK activity did not exert a significant effect on the expression of the majority of genes responsible for lignin biosynthesis. The present results indicate that cytosolic shikimate recycling is crucial to the monomeric composition of lignin rather than for lignin content. [ABSTRACT FROM AUTHOR]

In natural habitats, especially in arid areas, plants are often simultaneously exposed to multiple abiotic stresses, such as salt, osmotic and heat stresses. However, most analyses of gene expression in stress responses examine individual stresses. In this report, we compare gene expression in individual and combined stresses. We show that combined stress treatments with salt, mannitol and heat induce a unique pattern of gene expression that is not a simple merge of the individual stress responses. Under multiple stress conditions, expression of most heat and salt stress-responsive genes increased to levels similar to or higher than those measured in single stress conditions, but osmotic stress-responsive genes increased to lower levels. Genes up-regulated to higher levels under multiple stress condition than single stress conditions include genes for heat shock proteins, heat shock regulators and late embryogenesis abundant proteins ( LEAs), which protect other proteins from damage caused by stresses, suggesting their importance in multiple stress condition. Based on this analysis, we identify candidate genes for engineering crop plants tolerant to multiple stresses. [ABSTRACT FROM AUTHOR]

SUMMARY: Cell walls, especially secondary cell walls (SCWs), maintain cell shape and reinforce wood, but their structure and shape can be altered in response to gravity. In hardwood trees, tension wood is formed along the upper side of a bending stem and contains wood fiber cells that have a gelatinous layer (G‐layer) inside the SCW. In a previous study, we generated nst/snd quadruple‐knockout aspens (Populus tremula × Populus tremuloides), in which SCW formation was impaired in 99% of the wood fiber cells. In the present study, we produced nst/snd triple‐knockout aspens, in which a large number of wood fibers had thinner SCWs than the wild type (WT) and some had no SCW. Because SCW layers are always formed prior to G‐layer deposition, the nst/snd mutants raise interesting questions of whether the mutants can form G‐layers without SCW and whether they can control their postures in response to changes in gravitational direction. The nst/snd mutants and the WT plants showed growth eccentricity and vessel frequency reduction when grown on an incline, but the triple mutants recovered their upright growth only slightly, and the quadruple mutants were unable to maintain their postures. The mutants clearly showed that the G‐layers were formed in SCW‐containing wood fibers but not in those lacking the SCW. Our results indicate that SCWs are essential for G‐layer formation and posture control. Furthermore, each wood fiber cell may be able to recognize its cell wall developmental stage to initiate the formation of the G‐layer as a response to gravistimulation. [ABSTRACT FROM AUTHOR]

Summary: Wounding triggers de novo organogenesis, vascular reconnection and defense response but how wound stress evoke such a diverse array of physiological responses remains unknown.We previously identified AP2/ERF transcription factors, WOUND INDUCED DEDIFFERENTIATION1 (WIND1) and its homologs, WIND2, WIND3 and WIND4, as key regulators of wound‐induced cellular reprogramming in Arabidopsis. To understand how WIND transcription factors promote downstream events, we performed time‐course transcriptome analyses after WIND1 induction.We observed a significant overlap between WIND1‐induced genes and genes implicated in cellular reprogramming, vascular formation and pathogen response. We demonstrated that WIND transcription factors induce several reprogramming genes to promote callus formation at wound sites. We, in addition, showed that WIND transcription factors promote tracheary element formation, vascular reconnection and resistance to Pseudomonas syringae pv. tomato DC3000.These results indicate that WIND transcription factors function as key regulators of wound‐induced responses by promoting dynamic transcriptional alterations. This study provides deeper mechanistic insights into how plants control multiple physiological responses after wounding. [ABSTRACT FROM AUTHOR]

Lignin content and its molecular structure influence various wood characteristics. In this study, the anatomical and physicochemical properties of wood derived from a naturally occurring mulberry mutant deficient in cinnamyl alcohol dehydrogenase (CAD), a key enzyme in lignin biosynthesis, were analyzed using conventional staining assays on stem sections, length and width measurements of xylem fiber cells, wood pulping and saccharification assays, and sugar compositional analysis of extractive-free wood powder. The present data indicate that the mutation in the CAD gene leads to improved wood delignification efficiency, increased pulp yield under alkaline pulping conditions, and enhanced saccharification efficiency following alkaline pretreatment. This study opens up new avenues for the multipurpose use of the mulberry CAD-deficient mutant as a raw material for biorefinery processes, in addition to its traditional use as a favored feed for silkworms. [ABSTRACT FROM AUTHOR]

Leaf senescence is the final process of leaf development that involves the mobilization of nutrients from old leaves to newly growing tissues. Despite the identification of several transcription factors involved in the regulation of this process, the mechanisms underlying the progression of leaf senescence are largely unknown. Herein, we describe the proteasome-mediated regulation of class II ETHYLENE RESPONSE FACTOR (ERF) transcriptional repressors and involvement of these factors in the progression of leaf senescence in Arabidopsis (Arabidopsis thaliana). Based on previous results showing that the tobacco (Nicotiana tabacum) ERF3 (NtERF3) specifically interacts with a ubiquitin-conjugating enzyme, we examined the stability of NtERF3 in vitro and confirmed its rapid degradation by plant protein extracts. Furthermore, NtERF3 accumulated in plants treated with a proteasome inhibitor. The Arabidopsis class II ERFs AtERF4 and AtERF8 were also regulated by the proteasome and increased with plant aging. Transgenic Arabidopsis plants with enhanced expression of NtERF3, AtERF4, or AtERFS showed precocious leaf senescence. Our gene expression and chromatin immunoprecipitation analyses suggest that AtERF4 and AtERF8 targeted the EPITHIOSPECIFIER PROTEIN/EPITH1OSPECIFYING SENESCENCE REGULATOR gene and regulated the expression of many genes involved in the progression of leaf senescence. By contrast, an aterf4 aterf8 double mutant exhibited delayed leaf senescence. Our results provide insight into the important role of class II ERFs in the progression of leaf senescence. [ABSTRACT FROM AUTHOR]

In plants, basic helix-loop-helix (bHLH) transcription factors play important roles in the control of cell elongation. Two bHLH proteins, PACLOBTRAZOL RESISTANCE1 (PRE1) and Arabidopsis ILI1 binding bHLH1 (IBH1), antagonistically regulate cell elongation in response to brassinosteroid and gibberellin signaling, but the detailed molecular mechanisms by which these factors regulate cell elongation remain unclear. Here, we identify the bHLH transcriptional activators for cell elongation (ACEs) and demonstrate that PRE1, IBH1, and the ACEs constitute a triantagonistic bHLH system that competitively regulates cell elongation. In this system, the ACE bHLH transcription factors directly activate the expression of enzyme genes for cell elongation by interacting with their promoter regions. IBH1 negatively regulates cell elongation by interacting with the ACEs and thus interfering with their DNA binding. PRE1 interacts with IBH1 and counteracts the ability of IBH1 to affect ACEs. Therefore, PRE1 restores the transcriptional activity of ACEs, resulting in induction of cell elongation. The balance of triantagonistic bHLH proteins, ACEs, IBH1, and PRE1, might be important for determination of the size of plant cells. The expression of IBH1 and PRE1 is regulated by brassinosteroid, gibberellins, and developmental phase dependent factors, indicating that two phytohormones and phase-dependent signals are integrated by this triantagonistic bHLH system. [ABSTRACT FROM AUTHOR]

Abstract: Since tall fescue (Festuca arundinacea Schreb.) is an anemophilous (wind-pollinated) grass species, male sterility is strongly desired for transgenic tall fescue to prevent pollen dispersal. To create male-sterile tall fescue, we applied Chimeric REpressor gene-Silencing Technology (CRES-T) based on rice APETALA3 (AP3) and AGAMOUS (AG) orthologues that specify the formation of stamens. We fused the coding regions of rice AP3 orthologue SUPERWOMAN1 (SPW1), and rice AG orthologues, Os12g0207000, Os01g0886200 and OsMADS58, respectively with the artificial sequence encoding the modified EAR-like motif repression domain (SRDX). We first introduced Os12g0207000SRDX, Os01g0886200SRDX and OsMADS58SRDX into rice for evaluation of their abilities to induce male sterility. The transgenic rice expressing OsMADS58SRDX had reiterated formation of lodicule-like organs instead of stamens and carpel, a typical phenotype of ag mutant. Thus, we found that OsMADS58SRDX was most suitable for our purpose. Next, we introduced SPW1SRDX and OsMADS58SRDX into tall fescue. Although the transgenic tall fescue did not have the stamen alterations seen in SPW1SRDX and OsMADS58SRDX rice, they either produced no pollen or produced immature pollen; thus, the anthers were not dehiscent and the plants were male-sterile. In addition to the male sterility, SPW1SRDX tall fescue showed a cleistogamous (closed) phenotype in which anthers were not observed outside the glumes, with thin, abnormally elongated lodicules. Some lines of OsMADS58SRDX tall fescue showed a cleistogamous phenotype in which the lodicules were homeotically transformed into lemma-like organs. In both cases, cleistogamous phenotype was associated with morphological changes to the lodicules. We also obtained a mild phenotype of OsMADS58SRDX tall fescue, which exhibited only the male sterility. In this study, we produced novel male-sterile phenotypes using chimeric repressors and thus suggest CRES-T as a tool for transgenic improvement of forage and turf grasses. [Copyright &y& Elsevier]

The Arabidopsis thaliana NAC domain transcription factor VASCULAR-RELATED NAC-DOMAIN7 (VND7) acts as a master regulator of xylem vessel differentiation. To understand the mechanism by which VND7 regulates xylem vessel differentiation, we used a yeast two-hybrid system to screen for proteins that interact with VND7 and identified cDNAs encoding two NAC domain proteins, VND-INTERACTING1 (VNI1) and VNI2. Binding assays demonstrated that VNI2 effectively interacts with VND7 and the VND family proteins, VND1-5, as well as with other NAC domain proteins at lower affinity. VNI2 is expressed in both xylem and phloem cells in roots and inflorescence stems. The expression of VNI2 overlaps with that of VND7 in elongating vessel precursors in roots. VNI2 contains a predicted PEST motif and a C-terminally truncated VNI2 protein, which lacks part of the PEST motif, is more stable than full-length VNI2. Transient reporter assays showed that VNI2 is a transcriptional repressor and can repress the expression of vessel-specific genes regulated by VND7. Expression of C-terminally truncated VNI2 under the control of the VND7 promoter inhibited the normal development of xylem vessels in roots and aerial organs. These data suggest that VNI2 regulates xylem cell specification as a transcriptional repressor that interacts with VND proteins and possibly also with other NAC domain proteins. [ABSTRACT FROM AUTHOR]

Lateral organ traits in higher plants, such as lamina shape and trichome distribution, change gradually in association with shoot maturation. Regulation of this shoot maturation process in the vegetative phase has been extensively investigated, and members of the SQUAMOSA PROMOTER BINDING PROTEIN (SBP)-box family of transcription factors have been shown to be involved in this process. However, little is known about the regulation of shoot maturation in the reproductive phase. We analyzed SPL10, SPL11 and SPL2, which are closely related members of the SBP-box family in Arabidopsis. While cauline leaves had oblong lamina and few trichomes emerged on cauline leaves and flowers in wild-type plants, transgenic plants expressing a dominant repressor version of SPL10/11/2 had wide cauline leaves and many trichomes on their cauline leaves and flowers. These traits were similar to those observed at an earlier reproductive phase in wild-type plants. Loss-of-function mutants for spl10/11/2 showed similar phenotypes, indicating that SPL10, SPL11 and SPL2 redundantly control proper development of lateral organs in association with shoot maturation in the reproductive phase. In the vegetative phase, lamina shape was affected in SPL10 transgenic plants, while trichome distribution was not altered. This suggests partial regulation of shoot development in the vegetative phase by SPL10. Meanwhile, the wide cauline leaves observed in the transgenic plants and the mutants were similar to those of fruitfull (ful) mutants. We found that FUL expression in leaves increased with shoot maturation and changed in SPL10 transgenic plants. FUL may function in shoot maturation under the control of SBP-box proteins. [ABSTRACT FROM PUBLISHER]

Orchid gynostemium, the fused organ of the androecium and gynoecium, and ovule development are unique developmental processes. Two DROOPING LEAF / CRABS CLAW (DL / CRC) genes, PeDL1 and PeDL2, were identified from the Phalaenopsis orchid genome and functionally characterized. Phylogenetic analysis indicated that the most recent common ancestor of orchids contained the duplicated DL/CRC -like genes. Temporal and spatial expression analysis indicated that PeDL genes are specifically expressed in the gynostemium and at the early stages of ovule development. Both PeDL s could partially complement an Arabidopsis crc-1 mutant. Virus-induced gene silencing (VIGS) of PeDL1 and PeDL2 affected the number of protuberant ovule initials differentiated from the placenta. Transient overexpression of PeDL1 in Phalaenopsis orchids caused abnormal development of ovule and stigmatic cavity of gynostemium. PeDL1, but not PeDL2, could form a heterodimer with Phalaenopsis equestris CINCINNATA 8 (PeCIN8). Paralogous retention and subsequent divergence of the gene sequences of PeDL1 and PeDL2 in P. equestris might result in the differentiation of function and protein behaviors. These results reveal that the ancestral duplicated DL/CRC -like genes play important roles in orchid reproductive organ innovation. [ABSTRACT FROM AUTHOR]

In this function, "counterparts" of a particular I Arabidopsis i gene means flax and poplar genes that best-hit to the particular I Arabidopsis i gene in a Blast search. In this case, I Arabidopsis i genes whose counterparts in flax and poplar meet each search condition are extracted and shown with the counterparts in flax and poplar. Each gene in the network is labeled by its symbol or the gene symbol of the corresponding I Arabidopsis i gene if the flax/poplar gene does not have a symbol. Keywords: database; flax; plant fibers; poplar; tension wood; tertiary cell wall; transcriptome EN database flax plant fibers poplar tension wood tertiary cell wall transcriptome 512 515 4 06/18/21 20210715 NES 210715 Acknowledgements The authors thank Prof. M. Deyholos (University of British Columbia, Canada) who provided seeds of the I rdf i mutant and corresponding background cultivar that were used to analyze transcriptomes in a specific sample set from an unpublished study. [Extracted from the article]

Wolfberry Lycium, an economically important genus of the Solanaceae family, contains approximately 80 species and shows a fragmented distribution pattern among the Northern and Southern Hemispheres. Although several herbaceous species of Solanaceae have been subjected to genome sequencing, thus far, no genome sequences of woody representatives have been available. Here, we sequenced the genomes of 13 perennial woody species of Lycium, with a focus on Lycium barbarum. Integration with other genomes provides clear evidence supporting a whole-genome triplication (WGT) event shared by all hitherto sequenced solanaceous plants, which occurred shortly after the divergence of Solanaceae and Convolvulaceae. We identified new gene families and gene family expansions and contractions that first appeared in Solanaceae. Based on the identification of self-incompatibility related-gene families, we inferred that hybridization hotspots are enriched for genes that might be functioning in gametophytic self-incompatibility pathways in wolfberry. Extremely low expression of LOCULE NUBER (LC) and COLORLESS NON-RIPENING (CNR) orthologous genes during Lycium fruit development and ripening processes suggests functional diversification of these two genes between Lycium and tomato. The existence of additional flowering locus C-like MADS-box genes might correlate with the perennial flowering cycle of Lycium. Differential gene expression involved in the lignin biosynthetic pathway between Lycium and tomato likely illustrates woody and herbaceous differentiation. We also provide evidence that Lycium migrated from Africa into Asia, and subsequently from Asia into North America. Our results provide functional insights into Solanaceae origins, evolution and diversification. Cao, Li, et al. sequence 13 perennial woody plant species of Lycium, and specifically provide a draft assembly of L. ruthenicum and a chromosome-level assembly of L. barbarum, the wolfberry or Goji berry. From a phylogenetic tree the authors identify an ancient hexaploidization event, and report the evolution of gene families including fruit ripening, fruit coloration, polysaccharide synthesis and self-incompatibility within Solanaceae and the general biogeography of L. barbarum. [ABSTRACT FROM AUTHOR]

Land plants are a monophyletic group of photosynthetic eukaryotes that diverged from streptophyte algae about 470 million years ago. During both the alternating haploid and diploid stages of the life cycle, land plants form multicellular bodies. 1,2,3,4 The haploid multicellular body (gametophyte) produces progenitor cells that give rise to gametes and the reproductive organs. 5,6,7,8 In the liverwort Marchantia polymorpha , differentiation of the initial cells of gamete-producing organs (gametangia) from the gametophyte is regulated by MpBONOBO (MpBNB), a member of the basic helix-loop-helix (bHLH) transcription factor subfamily VIIIa. In Arabidopsis thaliana , specification of generative cells in developing male gametophytes (pollen) requires redundant action of BNB1 and BNB2. 9 Subfamily XI bHLHs, such as LOTUS JAPONICUS ROOTHAIRLESS LIKE1 (LRL1)/DEFECTIVE REGION OF POLLEN1 (DROP1) and LRL2/DROP2 in A. thaliana and the single LRL/DROP protein MpLRL in M. polymorpha , are the evolutionarily conserved regulators of rooting system development. 10 Although the role of LRL1 / DROP1 and LRL2 / DROP2 in gametogenesis remains unclear, their loss leads to the formation of abnormal pollen devoid of sperm cells. 11 Here, we show that BNBs and LRL/DROPs co-localize to gametophytic cell nuclei and form heterodimers. LRL1/DROP1 and LRL2/DROP2 act redundantly to regulate BNB expression for generative cell specification in A. thaliana after asymmetric division of the haploid microspore. Mp LRL is required for differentiation of MpBNB-expressing gametangium initial cells in M. polymorpha gametophytes. Our findings suggest that broadly expressed LRL/DROP stabilizes BNB expression, leading to the formation of an evolutionarily conserved bHLH heterodimer, which regulates germ cell differentiation in the haploid gametophyte of land plants. [Display omitted] • BNB and LRL/DROP form an evolutionarily conserved bHLH heterodimer for gametogenesis • LRL/DROPs are required for generative cell specification in Arabidopsis • Mp LRL is required for gametangium initial cell differentiation in Marchantia • Broadly expressed LRL/DROP stabilizes BNB expression in germ cells Land plants produce gametes in the haploid gametophyte. Saito et al. demonstrate that subfamily XI bHLHs LRL/DROPs are required for stable expression of subfamily VIIIa bHLHs BNBs, leading to the formation of evolutionarily conserved heterodimers that regulate the differentiation of germ cells in the gametophytes of land plants. [ABSTRACT FROM AUTHOR]