Project description:Walnut (Juglans regia L.) is an important nut fruit crop mainly grown for its high nutritional and medicinal value. In walnut fruit, the pellicle is the main source of polyphenols (such as proanthocyanidins), which are natural bioactive compounds but also cause astringency and bitterness for walnut fruit consumption. However, the gene regulatory networks of phenolic biosynthetic pathways remain largely unknown in walnut pellicles. Here, we performed RNA sequencing (RNA-seq) to identify differentially expressed genes (DEGs) associated with pellicle development in walnut. In this study, seven developmental stages (8-, 9-, 11-, 13-, 15-, 17-, and 19-week after pollination) of ‘Xinwen179’ pellicle tissues were harvested to conduct further transcriptome-wide profiles. Via RNA-seq, we explored several key DEGs involved in the phenolic biosynthetic pathway, such as dihydroflavonol-4-reductase (DFR), leucoanthocyanidin reductase (LAR), anthocyanidin synthase (ANS) and anthocyanidin reductase (ANR), which are dynamically expressed at developmental stages of the walnut pellicle. Taken together, our preliminary investigation on DEGs associated with pellicle development will not only elucidate the gene regulatory networks of the phenolic biosynthetic pathway for pellicle development, but also contribute to the broad spectrum of RNA-seq data resources for further genetic improvement of walnut.
Project description:Walnut anthracnose caused by Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. is a major disease affecting walnut production in China. Although the long non-coding RNAs (lncRNAs) are important for plant disease resistance , the molecular mechanisms underlying resistance to C. gloeosporioides in walnut remain poorly understood.The anthracnose-resistant F26 fruits from the B26 clone and the anthracnose susceptible F423 fruits from the 4-23 clone of walnut were used as the test materials. Specifically, we performed a comparative transcriptome analysis of F26 fruit bracts and F423 to identify differentially expressed LncRNAs (DELs) at five time-points (tissues at 0 hpi, pathological tissues at 24 hpi, 48 hpi, 72 hpi, and distal uninoculated tissues at 120 hpi). Compared with F423, a total of 14525 DELs were identified, including 10645 upregulated lncRNAs and 3846 downregulated lncRNAs in F26. The number of upregulated lncRNAs in F26 compared to in F423 was significantly higher at the early stages of C. gloeosporioides infection. A total of 5 modules related to disease resistance were screened by WGCNA and the target genes of lncRNAs were obtained. Bioinformatic analysis showed that the target genes of upregulated lncRNAs were enriched in immune-related processes during the infection of C. gloeosporioides , such as activation of innate immune response, defense response to bacterium, incompatible interaction and immune system process, and enriched in plant hormone signal transduction, phenylpropanoid biosynthesis and other pathways. And 124 known target genes for 96 hub lncRNAs were predicted, including 10 known resistance genes. The expression of 5 lncRNAs and 5 target genes was confirmed by qPCR, which was consistent with the RNA-seq data.The results of this study provide the basis for future functional characterizations of lncRNAs regarding the C. gloeosporioides resistance of walnut fruit bracts.
Project description:For tree crops, shortening juvenile phase is a vital strategy for early flowering that ensure to bear fruits in advance to enhance breeding efficiency. In walnut (Juglans regia L.), it usually takes 3-5 years for blooming, but the early flowering (EF) walnut can even flower in a year after planted. The juvenile phase of EF walnut is shorter than the late flowering (LF) walnut, which is more propitious to breeding efficiency. In this study, using RNA sequencing (RNA-seq) and microRNA-seq, we profiled transcriptome-wide identification of gene expression and microRNAs between EF and LF walnuts.
Project description:We showed previously that gallic acid is produced in walnut from 3-dehydroshikimate by a shikimate dehydrogenase (JrSkDH). This study focuses on the next step in the hydrolysable tannin pathway, the formation of 1-<i>O</i>-galloyl-β-D-glucose from the phenolic gallic acid and UDP glucose by a glycosyltransferase. JrGGT1 (UGT84A73) and JrGGT2 (UGT84A74) are predicted to be two such glycosyltransferases, which we expressed in tobacco plants. GC-MS analysis of the transgenic tobacco revealed moderate, yet significant alterations in plant secondary metabolism, such as depleted phenolic acids, including gallic acid. We postulate that these effects are due to JrGGT1 and JrGGT2 activity, as JrGGT orthologs glycosylate these phenolic compounds <i>in vitro</i>. Moreover, <i>JrGGT</i> expression in tobacco caused upregulation of shikimic acid pathway metabolites and differing responses in phenylpropanoids, such as phenolic acids and flavonoids. In transcriptome analysis of walnut pellicle tissues, both <i>JrGGT</i>s showed substantial and significant expression correlations with the gallic acid-producing <i>JrSkDH</i>s and were highly coexpressed with the genetic circuits constituting the shikimic acid and phenylpropanoid biosynthetic pathways. Verification of <i>JrGGT</i> gene expression by transcriptome analysis of 20 walnut tissues revealed striking similarities with that of the pellicle data, with the greatest expression in roots, wood, buds, and leaves of <i>Juglans regia</i> cv. Chandler: tissues that typically accumulate hydrolysable tannins. Like the transgenic tobacco, pellicle metabolomic analyses revealed that many phenylpropanoids correlated negatively with <i>JrGGT</i> expression, while shikimic acid pathway metabolites correlated positively with <i>JrGGT</i> expression. This research supports the hypothesis that JrGGT1 and JrGGT2 play non-trivial roles in metabolism of phenolic acids, flavonoids, and ostensibly, tannins.
Project description:In the present study, we found a new walnut germplasm from wild Juglans cathayensis population, which presented white husk that did not brown. We compared the transcriptome between the fresh-cut browning (control) and white husks of the Chinese walnut using Illumina HiSeq 4000 platform