Mulberry (Morus, Moraceae) is an important economic plant with nutritional, medicinal, and ecological values. Lignin in mulberry can affect the quality of forage and the saccharification efficiency of mulberry twigs. The availability of the Morus notabilis genome makes it possible to perform a systematic analysis of the genes encoding the 11 protein families specific to the lignin branch of the phenylpropanoid pathway, providing the core genes for the lignin toolbox in mulberry. We performed genome-wide screening, which was combined with de novo transcriptome data for Morus notabilis and Morus alba variety Fengchi, to identify putative members of the lignin gene families followed by phylogenetic and expression profile analyses. We focused on bona fide clade genes and their response to zinc stress were further distinguished based on expression profiles using RNA-seq and RT-qPCR. We finally identified 31 bona fide genes in Morus notabilis and 25 bona fide genes in Fengchi. The putative function of these bona fide genes was proposed, and a lignin toolbox that comprised 19 genes in mulberry was provided, which will be convenient for researchers to explore and modify the monolignol biosynthesis pathway in mulberry. We also observed changes in the expression of some of these lignin biosynthetic genes in response to stress caused by excess zinc in Fengchi and proposed that the enhanced lignin biosynthesis in lignified organs and inhibition of lignin biosynthesis in leaf is an important response to zinc stress in mulberry.
Phytophthora blight is one of the most serious diseases affecting melon (Cucumis melo) production. Due to the lack of highly resistant germplasms, the progress on disease-resistant research is slow. To understand the genetics of melon resistance to Phytophthora capsici, an F2 population containing 498 individuals was developed by crossing susceptible line E31 to highly resistant line ZQK9. Genetic analysis indicated that the resistance in ZQK9 was controlled by a dominant gene, tentatively named MePhyto. Through bulked-segregant analysis (BSA-Seq) and chromosome walking techniques, the MePhyto gene was mapped to a 52.44 kb interval on chromosome 12. In this region, there were eight genes and their expression patterns were validated by qRT-PCR. Among them, one wall-associated receptor kinase (WAK) gene MELO3C002430 was significantly induced in ZQK9 after P. capsici inoculation, but not in E31. Based on the non-synonymous mutation site in MELO3C002430, a cleaved amplified polymorphic sequence (CAPS) marker, CAPS2430, was developed and this maker was co-segregated with MePhyto in both F2 population and a collection of 36 melon accessions. Thus MELO3C002430 was considered as the candidate gene and CAPS2430 was a promising marker for marker-assisted selection (MAS) in breeding. These results lay a foundation for revealing the resistance mechanism of melon to P. capsici.
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