Project description:Grafting is a well-established practice for grapevine to facilitate propagation of productive and tolerant cultivars against several stress factors. It is also considered to be a suitable method for studying molecular aspects of root-to-shoot and/or shoot-to-root signaling events. So far, controlling only effect of rootstock over scion was investigated and root-to-shoot transcriptomic alterations were fallowed on the scions or graft interfaces. The objective of this study was to investigate transcriptomic and physiological influence of scion on the rootstock under drought stress. Therefore, drought tolerant 110R rootstock were firstly grafted with sultana seedless and tested under drought stress with its non-grafted counterpart. The results of treatment indicated that grafted 110R performed the highest root elongation under drought. We carried out a microarray based transcriptome analysis on the roots of grafted and non-grafted 110R to explain this drought derived interaction through scion-to-rootstock. The highest expression increase under drought was recorded for sugar (SWEET) and nitrate or di/tri-peptide (NRT1/ PTR FAMILY) transporter proteins. Expression level of these genes was more highly increased in grafted 110R than its non-grafted counterpart. This situation indicated their potential role in drought tolerance and scion/rootstock harmony. Overexpression of these transporters attributed to increased amount of released nutrient and nitrogen source from abscised leaves of sultana seedless under drought. Remobilization of these rich sources was suggested to chance transcriptomic response of rootstocks and enabled much better growth in grafted 110R. Other transcripts annotated to cell wall modification enzymes (chitinases), osmoregulator proteins (dehydrins, proline-glycine rich proteins) and secondary metabolites (stilbene synthase) were also more highly induced in grafted 110R. This is the first report indicating transcriptomic influence of scion on the grapevine rootstocks and representing the genes responsible in scion/rootstock harmony and drought tolerance.

Project description:Purpose: Grafting is a commonly used cultural practice to counteract salt stress and is especially important for vegetable production. However, it is not clear which metabolic processes and genes are involved in the response of tomato rootstocks to salt stress. Our goals is to elucidate the regulatory mechanism through which grafting enhances salt tolerance. Methods: The salt-sensitive tomato variety Zhongza 9 and the strongly salt-tolerant tomato rootstock variety QZ-006 (selected by the research group in the early stage) were used as experimental materials and were purchased from the Vegetable and Flower Institute of the Chinese Academy of Agricultural Sciences (Beijing, CHN) and Beijing Kaixingelin Agricultural Technology Co., Ltd. (Beijing, CHN)；The leaves of the seedlings of every sample was added to 5 mL of HNO3 (65%~68%) after they were heated in a microwave digestion system for 2~3 hours；RNA-seq libraries were sequenced on an Illumina HiSeq X Ten platform；qRT‒PCR was performed according to the instructions of a Fast Super EvaGreen qPCR Master Mix Kit (US Everbright®, Inc.)；The amino acid contents in the tomato leaves were calculated by the external standard method. The chlorophyll of the seedlings was extracted with acetone-ethanol (1:1) ；An indirect enzyme-linked immunosorbent assay (ELISA) was used to determine auxin (IAA), gibberellin (GA), cytokinin (ZR), brassinolide (BR), abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) contents, and kit purchased from ThermoFisher Scientific Co., Ltd. (USA). Endogenous ethylene (ETH) was collected, fixed and determined according to the methods of Ling (Ling et al.,2008) using a Shimadzu 2010 gas chromatograph equipped with a hydrogen flame ion detector. ETH standard gas was purchased from Sigma Company. Results: Compared with the NGS, the GSs were more salt tolerant, and the Na+ content in the leaves decreased significantly. Through transcriptome sequencing data analysis of 36 samples, we found that GSs exhibited more stable gene expression patterns, with a lower number of DEGs. WRKY and PosF21 transcription factors were significantly upregulated in the GSs compared to the NGSs. Moreover, the GSs presented more amino acids, a higher photosynthetic index and a higher content of growth-promoting hormones. The main differences between GSs and NGSs were in the expression levels of genes involved in the BR signalling pathway, with significant upregulation of XTHs. Conclusions: Our study demonstrates that grafting on salt tolerant rootstocks can bring different metabolic processes and transcription levels changes to scion leaves, thereby the scion leaves show stronger salt tolerance. This information provides new insight into the mechanism underlying tolerance to salt stress regulation and provides useful molecular biological basis for improving plant salt resistance.

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Tomato and potato

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