Chloroplast analysis of Zelkova schneideriana (Ulmaceae): genetic diversity, population structure, and conservation implications

Comparative Transcriptome Sequencing and Endogenous Phytohormone Content of Annual Grafted Branches of Zelkova schneideriana and Its Dwarf Variety HenTianGao

Zelkova schneideriana is a fast-growing tree species endemic to China. Recent surveys and reports have highlighted a continued decline in its natural populations; therefore, it is included in the Red List of Threatened Species by The International Union for Conservation of Nature. A new variety "HenTianGao" (H) has been developed with smaller plant height, slow growth, and lower branching points. In this study, we attempted to understand the differences in plant height of Z. schneideriana (J) and its dwarf variety H. We determined the endogenous hormone content in the annual grafted branches of both J and H. J exhibited higher gibberellic acid (GA)-19 and trans-Zeatin (tZ) levels, whereas H had higher levels of indole-3-acetic acid (IAA) catabolite 2-oxindole-3-acetic acid (OxIAA), IAA-Glu conjugate, and jasmonic acid (JA) (and its conjugate JA-Ile). The transcriptome comparison showed differential regulation of 20,944 genes enriched in growth and development, signaling, and metabolism-related pathways. The results show that the differential phytohormone level (IAA, JA, tZ, and GA) was consistent with the expression of the genes associated with their biosynthesis. The differences in relative OxIAA, IAA-Glu, GA19, trans-Zeatin, JA, and JA-Ile levels were linked to changes in respective signaling-related genes. We also observed significant differences in the expression of cell size, number, proliferation, cell wall biosynthesis, and remodeling-related genes in J and H. The differences in relative endogenous hormone levels, expression of biosynthesis, and signaling genes provide a theoretical basis for understanding the plant height differences in Z. schneideriana.

De novo transcriptome assembly and EST-SSR markers development for Zelkova schneideriana Hand.-Mazz. (Ulmaceae)

Zelkova schneideriana Hand.-Mazz. of the Ulmaceae family is a Tertiary relict and economically deciduous tree species endemic to Central and Southern China. In this study, we performed a transcriptome sequencing of Z. schneideriana using high-throughput sequencing approach to detect polymorphic expressed sequence tag-simple sequence repeats (EST-SSR) markers. A total of 3,235 microsatellite loci were detected from 53,517 unigenes. A set of 30 microsatellite markers were randomly selected to validate in 41 individuals from three populations, of which 10 were polymorphic. The number of alleles per locus ranged from 3 to 11. The observed heterozygosity and expected heterozygosity ranged from 0.366 to 0.829 and 0.439 to 0.848, respectively. These polymorphic SSR primers showed good transferability across different Zelkova species, and are valuable for future studies on genetic diversity, conservation, phylogeography, and species delimitation in Z. schneideriana, as well as other Zelkova species.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02968-5.