ABSTRACT
A plant parasite obligately parasitizing another plant parasite is referred to as epiparasite, which is extremely rare in angiosperms, and their complete plastome sequences have not been characterized to date. In this study, the complete plastomes of two flowering epiparasites: Phacellaria compressa and P. glomerata (Amphorogynaceae, Santalales) were sequenced. The plastomes of both species are of similar size, structure, gene content, and arrangement of genes to other hemiparasites in Santalales. Their plastomes were characterized by the functional loss of plastid-encoded NAD(P)H-dehydrogenase and infA genes, which strongly coincides with the general pattern of plastome degradation observed in Santalales hemiparasites. Our study demonstrates that the relatively higher level of nutritional reliance on the host plants and the reduced vegetative bodies of P. compressa and P. glomerata do not appear to cause any unique plastome degradation compared with their closely related hemiparasites.
Subject(s)
Genome, Plastid , Heterotrophic Processes , Santalaceae/genetics , Animals , Evolution, Molecular , Gene Deletion , NADPH Dehydrogenase/genetics , Plant Proteins/genetics , Polymorphism, Genetic , Santalaceae/metabolism , Santalaceae/physiologyABSTRACT
Most plants show remarkable developmental plasticity in the generation of diverse types of new organs upon external stimuli, allowing them to adapt to their environment. Haustorial formation in parasitic plants is an example of such developmental reprogramming, but its molecular mechanism is largely unknown. In this study, we performed field-omics using transcriptomics and metabolomics to profile the molecular switch occurring in haustorial formation of the root parasitic plant, Thesium chinense, collected from its natural habitat. RNA-sequencing with de novo assembly revealed that the transcripts of very long chain fatty acid (VLCFA) biosynthesis genes, auxin biosynthesis/signaling-related genes and lateral root developmental genes are highly abundant in the haustoria. Gene co-expression network analysis identified a network module linking VLCFAs and the auxin-responsive lateral root development pathway. GC-TOF-MS analysis consistently revealed a unique metabolome profile with many types of fatty acids in the T. chinense root system, including the accumulation of a 25-carbon long chain saturated fatty acid in the haustoria. Our field-omics data provide evidence supporting the hypothesis that the molecular developmental machinery used for lateral root formation in non-parasitic plants has been co-opted into the developmental reprogramming of haustorial formation in the linage of parasitic plants.
Subject(s)
Gene Expression Profiling , Metabolomics , Plant Roots/genetics , Plant Roots/metabolism , Santalaceae/anatomy & histology , Santalaceae/genetics , Gene Expression Regulation, Developmental , Gene Expression Regulation, Plant , Gene Regulatory Networks , Santalaceae/metabolism , Transcriptome/geneticsABSTRACT
In order to explore reasonable artificial cultivation pattern of Thesium chinense, the biological characteristics and nutrients change in the process of winter dormancy of T. chinense was studied. The phenological period of T. chinense was observed by using fixed-point notation and the starch grains changes were determined dynamically by PAS-vanadium iron hematoxylin staixjing method. Soluble sugar and starch content were measured by anthrone-sulfuric acid method and amylase activity was determined by DN'S method. The results showed that the normal life cycle of T. chinense was two years. T. chinense was growing by seed in the first year, but growing by the root neck bud in the second year. During the process of dormancy, starch and soluble sugar could mutual transformation in different periods. T. chinense had sufficient carbohydrate to maintain growth and also a lot of small molecules to improve their ability to fight against adversity.
Subject(s)
Plant Dormancy , Santalaceae/growth & development , Plant Leaves/chemistry , Plant Leaves/growth & development , Plant Leaves/metabolism , Plant Roots/chemistry , Plant Roots/growth & development , Plant Roots/metabolism , Plant Stems/chemistry , Plant Stems/growth & development , Plant Stems/metabolism , Santalaceae/chemistry , Santalaceae/metabolism , Seasons , Starch/analysis , Starch/metabolismABSTRACT
OBJECTIVE: To study the hemiparasitic mechanism of Thesium chinense. METHOD: The anatomical structure of T. chinense was studied by using paraffin slice and electron microscope slice. Chlorophyll content was measured by UV spectrometry. Foliar photosynthesis (P(n)) and gas exchange were measured by using a LI-6400 photosynthesis system. RESULT: Chloroplast possesses intact granal thylakoid system, lamella was strong. Vascular tissue of T. chinense was strong. Vessel aperture and its transport power were strong both in root and stem. There were many global haustoriums on lateral roots. Vascular tissues were strong inside haustorium, haustorial stylet penetrated epidermis and cortex of host root, and reached pith place, haustorial vessel was integrated with host root vessel. The maximum of P(n) of T. chinense reached 7.06 micromol x m(-2) x s(-1), its water use efficiency was lower, about 0.735 mmol x mol(-1), its transpiration varied notable in daytime and was relatively invariant at nighttime, and the value of daytime was greatly exceed that of nighttime. CONCLUSION: T. chinense despoils water and nutrition from its host by haustorium. T. chinense can mostly be independent as for C supply by photosynthesis.
