Consensus maps of cloned plant cuticle genes

Plant cuticle,which covers the plant surface,consists of waxes and cutins,and is associated with plant drought,cold,and salt resistance.Hitherto,at least 47 genes participating in the formation of plant cuticle have been cloned from Arabidopsis thaliana,Oryza sativa,Zea mays,Ricinus communis,Brassica napus,and Medicago truncatula;and about 85% of them encode proteins sharing above 50% identities with their rice homologous sequences.These cloned cuticle genes were mapped in silico on different chromosomes of rice and Arabidopsis,respectively.The mapping results revealed that plant cuticle genes were not evenly distributed in both genomes.About 40% of the mapped cuticle genes were located on chromosome 1 in Arabidopsis,while 20% of the mapped cuticle genes were located on chromosome 2 but none on chromosome 12 in rice.Some cloned plant cuticle genes have several rice homologous sequences,which might be produced by chromosomal segment duplication.The consensus map of cloned plant cuticle genes will provide important clues for the selection of candidate genes in a positional cloning of an unknown cuticle gene in plants.

Plant cuticles repress organ initiation and development during skotomorphogenesis in Arabidopsis

After germination in the dark,plants produce a shoot apical hook and closed cotyledons to protect the quiescent shoot apical meristem(SAM),which is critical for seedling survival during skotomorphogenesis.The factors that coordinate these processes,particularly SAM repression,remain enigmatic.Plant cuticles,multilayered structures of lipid components on the outermost surface of the aerial epidermis of all land plants,provide protection against desiccation and external environmental stresses.Whether and how cuticles regulate plant development are still unclear.Here,we demonstrate that mutants of BODYGUARD1(BDG1)and long-chain acyl-CoA synthetase2(LACS2),key genes involved in cutin biosynthesis,produce a short hypocotyl with an opened apical hook and cotyledons in which the SAM is activated during skotomorphogenesis.Light signaling represses expression of BDG1 and LACS2,as well as cutin biosynthesis.Transcriptome analysis revealed that cuticles are critical for skotomorphogenesis,particularly for the development and function of chloroplasts.Genetic and molecular analyses showed that decreased HOOKLESS1 expression results in apical hook opening in the mutants.When hypoxia-induced expression of LITTLE ZIPPER2 at the SAM promotes organ initiation in the mutants,the de-repressed expression of cell-cycle genes and the cytokinin response induce the growth of true leaves.Our results reveal previously unrecognized developmental functions of the plant cuticle during skotomorphogenesis and demonstrate a mechanism by which light initiates photomorphogenesis through dynamic regulation of cuticle synthesis to induce coordinated and systemic changes in organ development and growth during the skotomorphogenesis-to-photomorphogenesis transition.

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment, but sorption mechanism is still not fully understood. In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction. Toward this end, cuticular materials were isolated from the fruits of tomato by chemical method. The tomato cuticle sheet consisted of waxes （6.5 wt%）, cuticular monomer （69.5 wt%）, and polysaccharide （24.0 wt%）. Isotherms of 1-naphthol to the cuticular fractions were nonlinear （N value （0.82 - 0.90）） at the whole tested concentration ranges. The K∞/Kow ratios for bulk cuticle （TC1）, dewaxed cuticle （TC2）, cutin （TC4）, and desugared cuticle （TC5） were larger than unity, suggested that tomato bulk cuticle and cutin are much powerful sorption medium. Sorption capability of cutin （TC4） was 2.4 times higher than the nonsaponifiable fraction （TC3）. The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar （H-bonding） interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material. There was a linear negative trend between K∞ values and the amount of polysaccharides or fraction＇s polarities （（N＋O）/C）; while a linear positive relationship between K∞ values and the content ofcutin monomer （linear R^2 = 0.993） was observed for present in the cuticular fractions. Predominant sorbent of the hydrophobic organic compounds （HOCs） in the plant cuticular fraction was the cutin monomer, contributing to 91.7% of the total sorption of tomato bulk cuticle.

Petrology and organic geochemistry of the Baishaping and Damaidi Devonian cutinitic liptobioliths,west of the Kangdian Uplift,China

Devonian cutinitic liptobiolith is a special type of coal formed during the early evolutionary stage of land plants.The Baishaping and Damaidi Devonian coals are notable for their distinct papery,sheet-like texture,and unusually high cutinite content(>50%),belonging to typical cutinitic liptobiolith.They are bituminous coals and have a suppressed vitrinite reflectance.Compared with typical typeⅢkerogen,these liptobioliths are characterized by extremely high yields of volatile matter and high hydrogen contents owing to their enhanced cutinite contents.As indicated by pyrolysis and elemental analysis results,the Devonian cutinitic liptobioliths are dominated by typeⅠ-Ⅱkerogens and have an excellent potential to generate liquid hydrocarbons.The Baishaping cutinitic liptobioliths are mainly composed of ribbon-like thick-walled cutinites,with small amounts of thin-walled type.Vitrinite is only present in trace amounts and is dominated by telinite.Meanwhile,the Damaidi Devonian coals are primarily composed of ribbon-like thin-walled cutinites,followed by collotelinites which are usually sandwiched by cutinites.The different petrological characteristics of the Baishaping and Damaidi liptobioliths might indicate a structural variation in the coal-forming plant cuticles and two distinct coal-forming conditions.The molecular bio markers in the Devonian coals are mainly composed of C_(18)-C_(20)tetracyclic diterpenoids,which are assumed to be the dominant soluble constituent of the Devonian land-plant cuticles and might have played an important role in early land plant radiation.Other molecules include aromatic tetracyclic diterpenoids,3-5 ring polycyclic aromatic hydrocarbons and their methylated counterparts,and C_(16)-and C_(18)-monocarboxylic acids.n-Alkanes are present only in small amounts.The molecular composition of the cutinite-rich coals is unexpected,because cuticular waxes are one of the most important sources of n-alkanes.In general,the petrology and geochemistry of the Devonian cutinitic liptobiolith indicate a distinct structure and composition for the early land-plant cuticles,which is significantly different from that of the plant cuticles since Carboniferous.Devonian cutinitic liptobioliths are of great interest because of their unique petrography,geochemistry,coal-forming plants,and oil-prone potential.Studies on this unique coal type provide a better understanding of coal-forming plants,paleoenvironment,paleoclimate,and early land-plant evolution in the Devonian.