Control of Leaf Width by the APC/CTAD1-WL1-NAL1 Pathway in Rice

Leaf morphology is one of the most important features of the ideal plant architecture. However, the genetic and molecular mechanisms controlling leaf morphology in crops remain largely unknown, despite their central importance. Here we demonstrate that the APC/CTAD1-WL1-NAL1 pathway regulates leaf width in rice, and mutation of WL1 leads to width leaf variation. WL1 interacts with TAD1 and is degraded by APC/CTAD1, with the loss of TAD1 function resulting in narrow leaves. The WL1 protein directly binds to the regulatory region of NAL1 and recruits the corepressor TOPLESS-RELATED PROTEIN to inhibit NAL1 expression by down-regulating the level of histone acetylation of chromatin. Furthermore, biochemical and genetic analyses revealed that TAD1, WL1, and NAL1 function in a common pathway to control leaf width. Our study establishes an important framework for the APC/CTAD1-WL1-NAL1 pathway-mediated control of leaf width in rice and introduces novel perspectives for using this regulatory pathway for improving crop plant architecture.

Cytological, Biochemical, and Transcriptomic Analyses of a Novel Yellow Leaf Variation in a Paphiopedilum (Orchidaceae) SCBG COP15

The genus Paphiopedilum, belonging to the Orchidaceae, has high ornamental value. Leaf variations can considerably improve the economic and horticultural value of the orchids. In the study, a yellow leaf mutant of a Paphiopedilum hybrid named P. SCBG COP15 was identified during the in vitro plant culture process; however, little is known about their molecular mechanisms. For this, RNA-seq libraries were created and used for the transcriptomic profiling of P. SCBG COP15 and the yellow mutant. The Chl a, Chl b, and carotenoid contents in the yellow leaves decreased by approximately 75.99%, 76.92%, and 56.83%, respectively, relative to the green leaves. Decreased chloroplasts per cell and abnormal chloroplast ultrastructure were observed by electron microscopic investigation in yellowing leaves; photosynthetic characteristics and Chl fluorescence parameters were also decreased in the mutant. Altogether, 34,492 unigenes were annotated by BLASTX; 1,835 DEGs were identified, consisting of 697 upregulated and 1138 downregulated DEGs. HEMA, CRD, CAO, and CHLE, involved in Chl biosynthesis, were predicted to be key genes responsible for leaf yellow coloration. Our findings provide an essential genetic resource for understanding the molecular mechanism of leaf color variation and breeding new varieties of Paphiopedilum with increased horticultural value.

Variation in Leaf Morphology of Sago Trees (Metroxylon sagu) in South Borneo Province, Indonesia.

Natural populations of sago (Metroxylon sagu) in Indonesia show morphological variations in its organs, particularly the leaves. The existing variations resulted in sago type names provided by the locals. The sago plant types include Mahang, Buntal, Salak, Madang and Gandut. Sago leaves are economically important in Indonesia, mainly because they provide a potentially profitable and environment-friendly source of house roofing materials. Determining leaf variation among sago plants would provide information for a better way of choosing which among the current accessions/varieties of sago has the best leaf quality and production. Leaf variations in sago were recorded in shape, size, and color. The aim of this study are a) to compare differences in leaf morphology among sago types obtained from different geographic areas, and b) to determine whether these different sago types correspond to certain sago plant grouping. The qualitative and quantitative analysis showed variations in leaf characteristics of sago trees. Additionally, this study shows that based on leaf variations, the sago of South Borneo Province can be separated into two groups. The first group is Mahang and Gandut, which have long rachis, leaflets and leaves, and largest leaf area. The second group composed of Buntal, Salak and Madang accessions, which have short rachis and leaves, and smallest leaf area. Other results showed that there were characters that contributed significantly to the diversity of sago plants in the study area including spines, white stripe or banding on the rachis and petiole length. In line with our results, Mahang and Gandut accessions are the best accessions to be cultivated in the area, because they have wider leaves which support higher rates of photosynthesis. Further study should be conducted on phylogenetic using DNA sequencing to confirm divisions of the two sago groups.

Taxonomic relationships and population differentiation of the south-western Eurasian Zelkova species inferred in leaf morphology

The relict tree species Zelkova abelicea and Z. sicula (Ulmaceae) occur in Crete and Sicily, respectively. Zelkova abelicea grows in approximately 40 localities in the mountains of Crete, while Z. sicula has been found in only two stands in Sicily. We compared 25 morphological characters of the leaves of both species and used statistical methods (Tukey’stest, discrimination analysis, principal component analysis, agglomeration) to reveal the differences between these two species, their relation to Z. carpinifolia (the third Zelkova south-west Eurasian species), and between the leaves from different shoot types. Our study represents the first comparative biometric analysis of the three Zelkova species localized in the western edge of the current geographic range of the genus. We found that the species differed from each other both, in terms of leaf form characters and level of leaf variation. Zelkova carpinifolia was clearly different from Z. abelicea, while the two populations of Z. sicula, SIB and SIA, were more similar to Z. carpinifolia and Z. abelicea, respectively. The latter finding supports the results of recent molecular studies suggestingt he hybrid origin of Z. sicula. Zelkova abelicea, Z. sicula and Z. carpinifolia differ each other in the leaf characteristics and level of phenotypic variation.

Molecular and morphological analyses clarify species delimitation and reveal a new Betula species in section Costatae

Background and AimsDelineating closely related and morphologically similar species with overlapping ranges can be difficult. Here, we use section Costatae (genus Betula) as a model to resolve species and subspecies boundaries in four morphologically similar trees: Betula ashburneri, Betula costata, Betula ermanii and Betula utilis (including ssp. utilis, and diploid and tetraploid races of ssp. albosinensis).MethodsWe genotyped 298 individuals (20-80 per species) from 38 populations at 15 microsatellite markers and a subset of 34 individuals from 21 populations using restriction-site associated DNA sequencing (RAD-seq). Morphometric analysis was conducted to characterise leaf variation for a subset of 89 individuals.Key ResultsMolecular analyses and leaf morphology found little differentiation between B. ashburneri, diploid B. utilis ssp. albosinensis and some samples of B. utilis ssp. utilis suggesting that these should be treated as a single species. By contrast, tetraploid Betula utilis ssp. albosinensis was divided into two groups with group I genetically similar to B. utilis ssp. utilis based on SNPs and group II, a very distinct cluster, which we propose as a new species, namely, Betula buggsii. Phylogenomic analysis based on 2,285,620 SNPs show a well-supported monophyletic clade of B. buggsii, forming a sister with a well-supported clade of B. ashburneri, diploid B. albosinensis and some samples of B. utilis ssp. utilis. Morphologically, Betula buggsii is characterised by elongated lenticels and a distinct pattern of bark peeling. Betula buggsii is geographically restricted to the Qinling-Daba Mountains.ConclusionsOur study reveals six genetically distinguishable species: B. ashburneri, B. buggsii, B. costata, B. utilis ssp. utilis, B. utilis ssp. albosinensis and B. ermanii. Our research demonstrates an integrative approach in delimitating species using morphological and genetic samples from their nearly entire distributions. Analyses based on subsets of species’ distributions may lead to erroneous species or subspecies delineation.

Elliptical Fourier Descriptors of Leaf Outlines: A Tool to Discriminate Among Aquilaria Species (Thymelaeaceae)

Leaf shape analysis of three Aquilaria species was undertaken using Elliptical Fourier descriptors (EFD) within a research plan­ting in tropical Australia. This approach was taken to develop a method for discriminating the species in the absence of repro­ductive traits or genetic analysis and as a morphological scale of leaf variation. Leaf outlines were analysed to distinguish variability between species. Principal components analysis and canonical discriminant analysis were applied to group the spe­cies based on 25 Fourier descriptors. Four components were required to explain 78 % of the variance and the first and second canonical functions discriminated three groups of spe­cies therefore EFD was a useful approach for analysing leaf out­line variability and distinguish species in the genus Aquilaria. This approach provides a rapid method that could assist in the species identification in Aquilaria where reproductive traits are absent.