Regulation Of Leaf Development Research Articles

Comprehensive analysis of Cytokinin response factors revealed PagCRF8 regulates leaf development in Populus alba × P. glandulosa

Cytokinin response factors (CRFs) are a specialized group of APETALA2/Ethylene Responsive Factor (AP2/ERF) family transcription factors found exclusively in plants, where they play essential roles in responding to cytokinins and regulating plant development and stress responses. This study focused on the analysis of CRF family members in Populus trichocarpa and ‘84 K’ poplar (Populus alba × P. glandulosa), elucidating their evolutionary patterns and expression characteristics. Notably, compared to the 12 CRFs in Arabidopsis thaliana, only 11 members were identified in poplar, with five paralogous pairs generated from the whole-genome duplication events. And differential expression patterns were observed in pairs-2, 4, and 5, particularly highlighting the high expression of PagCRF8 in shoot apical and young leaves, as confirmed by promoter::GUS staining. Furthermore, overexpression of PagCRF8 in poplar led to distinct phenotypic changes, including leaf shrinkage, reduced leaf area, and an increased leaf length/width ratio. Microscopic analysis demonstrated irregular and enlarged leaf cells, elongated cells in leaf veins, and a reduction in trichomes on the leaf surface in response to PagCRF8 overexpression. In summary, this study provides a comprehensive understanding of the evolutionary and functional characteristics of the poplar CRF gene family, while also highlighting the involvement of PagCRF8 in controlling leaf development in poplar.

Arabidopsis SSL1 encoding AtMWFE subunit of mitochondrial complex I regulates leaf development and reactive oxygen species

Arabidopsis SSL1 encoding AtMWFE subunit of mitochondrial complex I regulates leaf development and reactive oxygen species

Cloning and expression pattern analysis of abscisic acid receptor gene McPYL4 in Mentha canadensis

Mentha canadensis is a traditional Chinese herb with great medicinal and economic value. Abscisic acid(ABA) receptor PYLs have important roles in plant growth and development and response to adversity. The M. canadensis McPYL4 gene was cloned, and its protein characteristics, gene expression, and protein interactions were analyzed, so as to provide genetic resources for genetic improvement and molecular design breeding for M. canadensis resistance. Therefore, the protein characteristics, subcellular localization, gene expression pattern, and protein interactions of McPYL4 were analyzed by bioinformatics analysis, transient expression of tobacco leaves, RT-qPCR, and yeast two-hybrid(Y2H) techniques. The results showed that the McPYL4 gene was 621 bp in length, encoding 206 amino acids, and its protein had the conserved structural domain of SRPBCC and was highly homologous with Salvia miltiorrhiza SmPYL4. McPYL4 protein was localized to the cell membrane and nucleus. The McPYL4 gene was expressed in all tissue of M. canadensis, with the highest expression in roots, followed by leaves, and it showed a pattern of up-regulation followed by down-regulation in leaves 1-8. In both leaves and roots, the McPYL4 gene responded to the exogenous hormones ABA, MeJA, and the treatments of drought, AlCl_3, NaCl, CdCl_2, and CuCl_2. Moreover, McPYL4 was up-regulated for expression in both leaves and roots under the MeJA treatment, as well as in leaves treated with AlCl_3 stress for 1 h, whereas McPYL4 showed a tendency to be down-regulated in both leaves and roots under other treatments. Protein interactions showed that McPYL4 interacted with AtABI proteins in an ABA-independent manner. This study demonstrated that McPYL4 responded to ABA, JA, and several abiotic stress treatments, and McPYL4 was involved in ABA signaling in M. canadensis and thus in the regulation of leaf development and various abiotic stresses in M. canadensis.

An Integrated Analysis of microRNAs and the Transcriptome Reveals the Molecular Mechanisms Underlying the Regulation of Leaf Development in Xinyang Maojian Green Tea (Camellia sinensis).

Xinyang Maojian (XYMJ) tea is one of the world's most popular green teas; the development of new sprouts directly affects the yield and quality of tea products, especially for XYMJ, which has hairy tips. Here, we used transcriptome and small RNA sequencing to identify mRNAs and miRNAs, respectively, involved in regulating leaf development in different plant tissues (bud, leaf, and stem). We identified a total of 381 conserved miRNAs. Given that no genomic data for XYMJ green tea are available, we compared the sequencing data for XYMJ green tea with genomic data from a closely related species (Tieguanyin) and the Camellia sinensis var. sinensis database; we identified a total of 506 and 485 novel miRNAs, respectively. We also identified 11 sequence-identical novel miRNAs in the tissues of XYMJ tea plants. Correlation analyses revealed 97 miRNA-mRNA pairs involved in leaf growth and development; the csn-miR319-2/csnTCP2 and miR159-csnMYB modules were found to be involved in leaf development in XYMJ green tea. Quantitative real-time PCR was used to validate the expression levels of the miRNAs and mRNAs. The miRNAs and target genes identified in this study might shed new light on the molecular mechanisms underlying the regulation of leaf development in tea plants.

Spatiotemporal miRNA and transcriptomic network dynamically regulate the developmental and senescence processes of poplar leaves.

Poplar is an important afforestation and urban greening species. Poplar leaf development occurs in stages, from young to mature and then from mature to senescent; these are accompanied by various phenotypic and physiological changes. However, the associated transcriptional regulatory network is relatively unexplored. We first used principal component analysis to classify poplar leaves at different leaf positions into two stages: developmental maturity (the stage of maximum photosynthetic capacity); and the stage when photosynthetic capacity started to decline and gradually changed to senescence. The two stages were then further subdivided into five intervals by gene expression clustering analysis: young leaves, the period of cell genesis and functional differentiation (L1); young leaves, the period of development and initial formation of photosynthetic capacity (L3-L7); the period of maximum photosynthetic capacity of functional leaves (L9-L13); the period of decreasing photosynthetic capacity of functional leaves (L15-L27); and the period of senescent leaves (L29). Using a weighted co-expression gene network analysis of regulatory genes, high-resolution spatiotemporal transcriptional regulatory networks were constructed to reveal the core regulators that regulate leaf development. Spatiotemporal transcriptome data of poplar leaves revealed dynamic changes in genes and miRNAs during leaf development and identified several core regulators of leaf development, such as GRF5 and MYB5. This in-depth analysis of transcriptional regulation during leaf development provides a theoretical basis for exploring the biological basis of the transcriptional regulation of leaf development and the molecular design of breeding for delaying leaf senescence.

Light and temperature regulation of leaf morphogenesis in Arabidopsis.

Leaves are the main photosynthetic organs in plants, and their anatomy is optimized for light interception and gas exchange. Although each species has a characteristic leaf anatomy, which depends on the genotype, leaves also show a large degree of developmental plasticity. Light and temperature regulate leaf development from primordia differentiation to late stages of blade expansion. While the molecular mechanisms of light and temperature signaling have been mostly studied in seedlings, in the latest years, research has focused on leaf development. Here, I will describe the latest work carried out in the environmental regulation of Arabidopsis leaf development, comparing signaling mechanisms between leaves and seedlings, highlighting the new discoveries, and pointing out the most exciting open questions.

Expressing a Short Tandem Target Mimic (STTM) of miR164b/e-3p enhances poplar leaf serration by co-regulating the miR164–NAC module

MicroRNAs (miRNAs) are short non-coding RNAs (21–24 nt) that play important roles in plant growth and development. The miR164 family is highly conserved in plants and the miR164–NAM/ATAF/CUC (NAC) module is validated to regulate leaf and flower development, lateral root initiation and stress response. However, our knowledge of its role in Populus remains limited. In this study, two mature miRNA species, miR164e-5p and miR164e-3p, were identified in Populus deltoides. Their nucleotide sequences were identical to those of miR164a/b/c/d/e-5p and miR164b/e-3p in P. tremula × P. alba clone 717-1B4 (hereinafter poplar 717), respectively. Transgenic plants of poplar 717, including overexpression lines (35S::pri-miR164e) and Short Tandem Target Mimic lines (STTM-miR164a-d,e-5p and STTM-miR164b/e-3p), were generated to study the roles of miR164e-5p and miR164e-3p in poplar. Compared with poplar 717, the leaf margins of 35S::pri-miR164e lines were smoother, the leaves of STTM-miR164b/e-3p line were more serrated, while the leaf morphology of STTM-miR164a-d,e-5p lines had no obvious change. In addition, both 35S::pri-miR164e and STTM-miR164b/e-3p plants had a dwarf phenotype. Expressions of miR164a-d,e-5p target genes, including PtaCUC2a, PtaCUC2b and PtaORE1, was significantly reduced in the apex of 35S::pri-miR164e lines. Green fluorescent protein (GFP) reporter assay showed that PtaCUC2a/2b and PtaORE1 were cleaved by miR164a-d,e-5p, and the cleavage was inhibited by STTM-miR164b/e-3p. Therefore, miR164b/e-3p may cooperate with miR164a-d,e-5p to regulate certain NAC members, such as PtaCUC2a/2b and PtaORE1, thereby regulating leaf development and plant growth in poplar. Our findings add new insights into the mechanisms by which the miR164–NAC module regulates plant development.

Genome-Wide Identification and Expression Analysis of the TCP Genes in Jatropha curcas L. Reveals Its Roles in Involvement of Leaf Shape

Jatropha curcas var. nigroviensrugosus CV Yang (Jn) exhibits wrinkled leaves and higher flowering and fruiting rates compared to Jatropha curcas L. (Jc). Teosinte branched1/Cincinnata/Proliferating cell factors (TCPs) are known to play crucial roles in plant development and physiological processes. However, it remains unknown whether or not the TCP gene family regulates in leaf development of Jc and Jn. Here, we systematically performed a genome-wide analysis of the Jc TCP family and investigated the differences in the expression of TCP in different leaf morphologies. In total, our results showed that 18 TCP members were identified in the whole genome sequence of Jatropha curcas L.; Jc TCP genes were classified into two categories by phylogenetic tree construction, among which there were 11 members in the Class I subfamily, seven members in the Class Ⅱ subfamily. It was shown that 12 members of Jc TCP genes were located at the seven chromosomes, and proteins belonging to the same TCP group exhibit higher similarity than those from different groups. Furthermore, the expression profiles of 15 TCP genes were discovered at different leaf developmental stages of Jc and Jn. Jc TCP 4, Jc TCP 5, Jc TCP 8, Jc TCP 13, Jc TCP 14, and Jc TCP 16 showed significantly different expressions, and can be used as candidate genes for regulating leaf development. Therefore, the TCP genes play important roles in regulating the leaf development in Jc, and the manipulation of Jc TCP genes can potentially be an important tool used for the genetic improvement of the leaf.

All together now: Cellular and molecular aspects of leaf development in lycophytes, ferns, and seed plants

Recent advances in plant developmental genetics together with rapid accumulation of transcriptomic data on plants from divergent lineages provide an exciting opportunity to explore the evolution of plant morphology. To understand leaf origin in sporophytes of land plants, we have combined the available molecular and structural data on development of leaves with different morphologies in different plant lineages: clubmosses, spikemosses, leptosporangiate ferns, ophioglossioid ferns, marattioid ferns, whisk ferns, horsetails, and conifers. Specifically, we address the peculiarities of proximo-distal, ad/abaxial, and lateral development; presence/absence of mesophyll differentiation into palisade and spongy parenchyma; and type of leaf vascular bundles (collateral and bicollateral). Furthermore, taxon-specific and morphology-specific features of leaf development are considered in the context of the organization of shoot apical meristems (SAMs)—monoplex, simplex, or duplex—that produce leaf primordia. The data available imply that cellular patterns of leaf initiation correlate strongly with the structure of the SAMs but not with further leaf development or morphology. The later stages of leaf development are neither correlated with SAM structure nor with taxonomy. Occurrence and, if available, patterns of expression of homologs of the angiosperm genes responsible for the development of adaxial (ARPandC3HDZ) and abaxial (YABBYandKANADI) leaf domains, or establishment of the leaf marginal meristem (WOX) are discussed. We show that there is no correlation in the set of homologs of TFs that regulate abaxial and adaxial leaf domain development between leaves containing only spongy and no palisade mesophyll (of spikemosses, clubmosses, whisk ferns, horsetails, and most conifers), and leaves differentiated into palisade and spongy mesophyll (of leptosporangiate ferns,Ginkgo,Gnetum, and angiosperms). Expression of three out of four regulators of leaf development in primordia of both leaves and sporangia—C3HDZin spikemosses and whisk ferns,YABBYin clubmosses andKANADIin spikemosses and horsetails—indicates that a sporangium developmental program could have been co-opted as a “precursor program” for the origin of microphylls and euphylls. Additionally, expression of leaf development regulators in SAMs of spikemosses (ARP,C3HDZ, andKANADI), clubmosses (YABBY), leptosporangiate ferns (C3HDZ), and horsetails (C3HDZandKANADI) indicates that at least some mechanisms of SAM regulation were co-opted as well in the pre-program of leaf precursors.

The Roles of Gibberellins in Regulating Leaf Development

Plant growth and development are correlated with many aspects, including phytohormones, which have specific functions. However, the mechanism underlying the process has not been well elucidated. Gibberellins (GAs) play fundamental roles in almost every aspect of plant growth and development, including cell elongation, leaf expansion, leaf senescence, seed germination, and leafy head formation. The central genes involved in GA biosynthesis include GA20 oxidase genes (GA20oxs), GA3oxs, and GA2oxs, which correlate with bioactive GAs. The GA content and GA biosynthesis genes are affected by light, carbon availability, stresses, phytohormone crosstalk, and transcription factors (TFs) as well. However, GA is the main hormone associated with BR, ABA, SA, JA, cytokinin, and auxin, regulating a wide range of growth and developmental processes. DELLA proteins act as plant growth suppressors by inhibiting the elongation and proliferation of cells. GAs induce DELLA repressor protein degradation during the GA biosynthesis process to control several critical developmental processes by interacting with F-box, PIFS, ROS, SCLl3, and other proteins. Bioactive GA levels are inversely related to DELLA proteins, and a lack of DELLA function consequently activates GA responses. In this review, we summarized the diverse roles of GAs in plant development stages, with a focus on GA biosynthesis and signal transduction, to develop new insight and an understanding of the mechanisms underlying plant development.

Overexpression of Mtr-miR319a Contributes to Leaf Curl and Salt Stress Adaptation in Arabidopsis thaliana and Medicago truncatula.

Salt stress is a worldwide agronomic issue that limits crop yield and quality. Improving salt stress tolerance via genetic modification is the most efficient method to conquer soil salinization problems in crops. Crop miRNAs have been declared to be tightly associated with responding and adapting to salt stress and are advantageous for salt tolerance modification. However, very few studies have validated vital salt tolerance miRNAs and coupled potent target genes in Medicago species, the most economically important forage legume species. In this study, Mtr-miR319a, a miRNA that was identified from the previous next-generation sequencing assay of salt-treated Medicago truncatula, was overexpressed in M. truncatula and Arabidopsis thaliana, inducing the curly leaves and salt stress tolerance phenotypes. Combining the elevated expression level of Mtr-miR319a in the M. truncatula overexpression lines under normal and salt-treatment conditions, the regulatory roles of Mtr-miR319a in leaf development and salt stress adaptation were demonstrated. Several predicted target genes of Mtr-miR319a were also regulated by Mtr-miR319a and were associated with the aforementioned phenotypes in M. truncatula plants, most notably MtTCP4. Our study clarified the functional role of Mtr-miR319a and its target genes in regulating leaf development and defending salt stress, which can help to inform crop breeding efforts for improving salt tolerance via genetic engineering.

Mutation of Leaf Senescence 1 Encoding a C2H2 Zinc Finger Protein Induces ROS Accumulation and Accelerates Leaf Senescence in Rice.

Premature senescence of leaves causes a reduced yield and quality of rice by affecting plant growth and development. The regulatory mechanisms underlying early leaf senescence are still unclear. The Leaf senescence 1 (LS1) gene encodes a C2H2-type zinc finger protein that is localized to both the nucleus and cytoplasm. In this study, we constructed a rice mutant named leaf senescence 1 (ls1) with a premature leaf senescence phenotype using CRISPR/Cas9-mediated editing of the LS1 gene. The ls1 mutants exhibited premature leaf senescence and reduced chlorophyll content. The expression levels of LS1 were higher in mature or senescent leaves than that in young leaves. The contents of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were significantly increased and catalase (CAT) activity was remarkably reduced in the ls1 plants. Furthermore, a faster decrease in pigment content was detected in mutants than that in WT upon induction of complete darkness. TUNEL and staining experiments indicated severe DNA degradation and programmed cell death in the ls1 mutants, which suggested that excessive ROS may lead to leaf senescence and cell death in ls1 plants. Additionally, an RT-qPCR analysis revealed that most senescence-associated and ROS-scavenging genes were upregulated in the ls1 mutants compared with the WT. Collectively, our findings revealed that LS1 might regulate leaf development and function, and that disruption of LS1 function promotes ROS accumulation and accelerates leaf senescence and cell death in rice.

The B-box transcription factor IbBBX29 regulates leaf development and flavonoid biosynthesis in sweet potato.

Plant flavonoids are valuable natural antioxidants. Sweet potato (Ipomoea batatas) leaves are rich in flavonoids, regenerate rapidly, and can adapt to harsh environments, making them an ideal material for flavonoid biofortification. Here, we demonstrate that the B-box (BBX) family transcription factor IbBBX29 regulates the flavonoid contents and development of sweet potato leaves. IbBBX29 was highly expressed in sweet potato leaves and significantly induced by auxin (IAA). Overexpression of IbBBX29 contributed to a 21.37%-70.94% increase in leaf biomass, a 12.08%-21.85% increase in IAA levels, and a 31.33%-63.03% increase in flavonoid accumulation in sweet potato, whereas silencing this gene produced opposite effects. Heterologous expression of IbBBX29 in Arabidopsis (Arabidopsis thaliana) led to a dwarfed phenotype, along with enhanced IAA and flavonoid accumulation. RNA-seq analysis revealed that IbBBX29 modulates the expression of genes involved in the IAA signaling and flavonoid biosynthesis pathways. Chromatin immunoprecipitation-quantitative polymerase chain reaction and electrophoretic mobility shift assay indicated that IbBBX29 targets key genes of IAA signaling and flavonoid biosynthesis to activate their expression by binding to specific T/G-boxes in their promoters, especially those adjacent to the transcription start site. Moreover, IbBBX29 physically interacted with developmental and phenylpropanoid biosynthesis-related proteins, such as AGAMOUS-LIKE 21 protein IbAGL21 and MYB308-like protein IbMYB308L. Finally, overexpressing IbBBX29 also increased flavonoid contents in sweet potato storage roots. These findings indicate that IbBBX29 plays a pivotal role in regulating IAA-mediated leaf development and flavonoid biosynthesis in sweet potato and Arabidopsis, providing a candidate gene for flavonoid biofortification in plants.

Cotton (Gossypium hirsutum) VIRMA as an N6-Methyladenosine RNA Methylation Regulator Participates in Controlling Chloroplast-Dependent and Independent Leaf Development.

N6-methyladenosine (m6A) is one of the most abundant internal modifications of mRNA, which plays important roles in gene expression regulation, and plant growth and development. Vir-like m6A methyltransferase associated (VIRMA) serves as a scaffold for bridging the catalytic core components of the m6A methyltransferase complex. The role of VIRMA in regulating leaf development and its related mechanisms have not been reported. Here, we identified and characterized two upland cotton (Gossypium hirsutum) VIRMA genes, named as GhVIR-A and GhVIR-D, which share 98.5% identity with each other. GhVIR-A and GhVIR-D were ubiquitously expressed in different tissues and relatively higher expressed in leaves and main stem apexes (MSA). Knocking down the expression of GhVIR genes by the virus-induced gene silencing (VIGS) system influences leaf cell size, cell shape, and total cell numbers, thereby determining cotton leaf morphogenesis. The dot-blot assay and colorimetric experiment showed the ratio of m6A to A in mRNA is lower in leaves of GhVIR-VIGS plants compared with control plants. Messenger RNA (mRNA) high-throughput sequencing (RNA-seq) and a qRT-PCR experiment showed that GhVIRs regulate leaf development through influencing expression of some transcription factor genes, tubulin genes, and chloroplast genes including photosystem, carbon fixation, and ribosome assembly. Chloroplast structure, chlorophyll content, and photosynthetic efficiency were changed and unsuitable for leaf growth and development in GhVIR-VIGS plants compared with control plants. Taken together, our results demonstrate GhVIRs function in cotton leaf development by chloroplast dependent and independent pathways.

The PagKNAT2/6b-PagBOP1/2a Regulatory Module Controls Leaf Morphogenesis in Populus.

Leaf morphogenesis requires precise regulation of gene expression to achieve organ separation and flat-leaf form. The poplar KNOTTED-like homeobox gene PagKNAT2/6b could change plant architecture, especially leaf shape, in response to drought stress. However, its regulatory mechanism in leaf development remains unclear. In this work, gene expression analyses of PagKNAT2/6b suggested that PagKNAT2/6b was highly expressed during leaf development. Moreover, the leaf shape changes along the adaxial-abaxial, medial-lateral, and proximal-distal axes caused by the mis-expression of PagKNAT2/6b demonstrated that its overexpression (PagKNAT2/6b OE) and SRDX dominant repression (PagKNAT2/6b SRDX) poplars had an impact on the leaf axial development. The crinkle leaf of PagKNAT2/6b OE was consistent with the differential expression gene PagBOP1/2a (BLADE-ON-PETIOLE), which was the critical gene for regulating leaf development. Further study showed that PagBOP1/2a was directly activated by PagKNAT2/6b through a novel cis-acting element “CTCTT”. Together, the PagKNAT2/6b-PagBOP1/2a module regulates poplar leaf morphology by affecting axial development, which provides insights aimed at leaf shape modification for further improving the drought tolerance of woody plants.

CiKN1 and CiKN6 are involved in leaf development in citrus by regulating CimiR164.

SUMMARYLeaf shape is an important agronomic trait that is involved in plant photosynthesis, flowering, disease resistance, and yield. In recent years, many leaf shape‐related genes have been identified in model plants, but the precise regulatory network of leaf shape development remains unclear, particularly in woody plants. Transcriptome analysis of trifoliate orange and lemon leaves revealed that two citrus Knotted1‐like (CiKN1 and CiKN6) genes might participate in leaf development. Overexpression of CiKN1 displays lobed leaves in simple leaf Arabidopsis and lemon. Further protein interaction analysis revealed that CiKN6 interacted with CiKN1, whose overexpression resulted in deeper lobed leaves in transgenic Arabidopsis and lemon. Suppressing CiKN6 expression also affected the development of lemon leaves. Furthermore, we found that the CiKN1–CiKN6 complex specifically binds to the citrus miR164a promoter and suppresses its expression. In addition, a SQUAMOSA promoter binding protein‐like (SPL) gene (CiSPL11) was identified using yeast one‐hybrid assays and was found to promote CiKN6 transcription by binding to its promoter. Transgenic Arabidopsis showed that CiSPL11 might be involved in the development of citrus leaves. These results suggested that the CiKN1–CiKN6 complex and miR164a interact to regulate leaf development in citrus.

CRISPR-Cas9-mediated mutagenesis of the SlSRM1-like gene leads to abnormal leaf development in tomatoes

BackgroundLeaves, which are the most important organs of plants, can not only fix carbon sources through photosynthesis, but also absorb nutrients through transpiration. Leaf development directly determines the growth, flowering and fruiting of plants. There are many factors that affect leaf development, such as the growth environment, gene expression, and hormone synthesis. In this study, tomatoes were used to study the role of the transcription factor Solanum lycopersicum salt-related MYB1-like (SlSRM1-like) in the development of tomato leaves.ResultsLoss-of-function of the SlSRM1-like gene mediated by clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR-associated 9 (Cas9) resulted in abnormal tomato leaf morphology, including thinner leaves, wrinkled edges, raised veins, disordered edge veins, and left and right asymmetry. An analysis of the transcription levels of genes related to leaf development revealed that the expression of these genes was significantly altered in the SlSRM1-like mutants (SlSRM1-like-Ms). Moreover, the SlSRM1-like gene was expressed at higher transcription levels in young tissues than in old tissues, and its expression was also induced in response to auxin. In addition, the transcription levels of genes related to the auxin pathway, which regulates tomato growth and development, were severely affected in the SlSRM1-like-Ms. Therefore, it is hypothesized that the SlSRM1-like gene functions in the regulation of tomato leaf development through the auxin-related pathway.ConclusionsIn this study, we successfully knocked out the SlSRM1-like gene in the tomato variety Ailsa Craig using CRISPR technology and found that knockout of the SlSRM1-like gene resulted in abnormal development of tomato leaves. Further research indicated that SlSRM1-like regulated tomato leaf development through auxin-related pathways. The results provide an important reference for the functional study of other SRM1-like genes in plants and provide new insights into the regulation of leaf development in tomato and other plants.

Roles of YABBY tanscription factors in the regulation of leaf development and abiotic stress responses in <i>Camellia sinensis</i>

The formation of leaf polarity directly determines the development of leaf spreading and type, and affects the physiological functions of photosynthesis, transpiration and stress resistance of plants. Many famous Chinese teas are highly dependent on the morphological characteristics and size of the tea leaves. To date, there have been few reports on the establishment of tea leaf polarity and leaf type development. The plant-specific transcription factor YABBY family gene has been reported to be involved in the formation of leaf polarity and growth. Herein we describe the isolation and functional characterization of transcription factor YABBY genes of the tea plant (<i>Camellia sinensis</i>). Six YABBY transcription factors were isolated from tea plants and classified into five clusters in the protein phylogenetic tree. Among them, <i>CsFILa</i> and <i>CsFILb</i> were highly expressed in buds and mature petals, and their expression decreased with the stage of leaf development. The Arabidopsis transgenic lines of <i>CsFILa</i> and <i>CsFILb</i> showed abaxial curled and long-narrow leaves. The above results indicated that <i>CsFILa</i> and <i>CsFILb</i> regulated the leaf growth of tea plants. The growth and expansion rate of leaf on the picked shoots decreased significantly after being plucked from tea plants, especially those suffering from drought stress. In this process, <i>CsFILa</i> expression levels decreased 60%−80% compared to the control. These data indicated YABBY genes play important roles in the leaf development of <i>Camellia sinensis</i>.

The FBA Motif-Containing Protein NpFBA1 Causes Leaf Curling and Reduces Resistance to Black Shank Disease in Tobacco

Plant leaf morphology has a great impact on plant drought resistance, ornamental research and leaf yield. In this study, we identified a new gene in Nicotiana plumbaginifolia, NpFBA1, that causes leaf curl. The results show that the NpFBA1 protein contains only one unique F-box associated (FBA) domain and does not have an F-box conserved domain. Phylogenetic analysis placed this gene and other Nicotiana FBA genes on a separate branch, and the NpFBA1 protein localized to the nucleus and cytoplasm. The expression of NpFBA1 was induced by black shank pathogen (Phytophthora parasitica var. nicotianae) infection and treatment with salicylic acid (SA) and methyl jasmonate (MeJA). NpFBA1-overexpressing transgenic lines showed leaf curling and aging during the rosette phase. During the bolting period, the leaves were curly and rounded, and the plants were dwarfed. In addition, NpFBA1-overexpressing lines were more susceptible to disease than wild-type (WT) plants. Further studies revealed that overexpression of NpFBA1 significantly downregulated the expression of auxin response factors such as NtARF3 and the lignin synthesis genes NtPAL, NtC4H, NtCAD2, and NtCCR1 in the leaves. In conclusion, NpFBA1 may play a key role in regulating leaf development and the response to pathogen infection.

NARROW AND DWARF LEAF 1, the Ortholog of Arabidopsis ENHANCER OF SHOOT REGENERATION1/DORNRÖSCHEN, Mediates Leaf Development and Maintenance of the Shoot Apical Meristem in Oryza sativa L.

The molecular basis for leaf development, a major focus in developmental biology, remains unclear in the monocotyledonous grass, rice (Oryza sativa). Here, we performed a mutant screen in rice and identified an AP2-type transcription factor family protein, NARROW AND DWARF LEAF1 (NDL1). NDL1 is the ortholog of Arabidopsis thaliana (subsequently called Arabidopsis) ENHANCER OF SHOOT REGENERATION1 (ESR1)/DORNRÖSCHEN (DRN) and mediates leaf development and maintenance of the shoot apical meristem (SAM). Loss of function of NDL1 results in bladeless leaves and SAMs that are flat, rather than dome-shaped, and lack cell proliferation activity. This loss of function also causes reduced auxin signaling. Moreover, as is the case with Arabidopsis ESR1/DRN, NDL1 plays crucial roles in shoot regeneration. Importantly, we found that NDL1 is not expressed in the SAM but is expressed in leaf primordia. We propose that NDL1 cell autonomously regulates leaf development, but non-cell autonomously regulates SAM maintenance in rice.