De novo Characterization of the Platycladus orientalis Transcriptome and Analysis of Photosynthesis-Related Genes during Aging

Abstract

In China, Platycladus orientalis has a lifespan of thousands of years. The long lifespan of these trees may be relevant for the characterization of plant aging at the molecular level. However, the molecular mechanism of the aging process of P. orientalis is still unknown. To explore the relationship between age and growth of P. orientalis, we analyzed physiological changes during P. orientalis senescence. The malondialdehyde content was greater in 200-, 700-, and 1100-year-old ancient trees than in 20-year-old trees, whereas the peroxidase and superoxide dismutase activities, as well as the soluble protein content, exhibited the opposite trend. Furthermore, we performed a de novo transcriptome assembly using RNA-Seq and obtained 48,044 unigenes with an average length of 896 bp. A total of 418 differentially expressed genes were identified in different stages of aging of P. orientalis. Clustering analysis revealed distinct timepoints at which the oxidation–reduction and photosynthesis pathways changed. Eight clusters with distinct expression patterns were identified. The expression levels of photosynthesis-, oxidation–reduction-, and transporter-related genes were down-regulated, whereas those of transcription-, signaling-, and senescence-related genes were up-regulated during aging. In addition, consistent with the most obviously down-regulated genes of photosynthesis-related genes, the photosynthetic indexes including chlorophyll a and b levels decreased steadily during P. orientalis aging. This study combined transcriptome with physiological and biochemical data, revealing potential candidate genes influencing senescence during P. orientalis aging.

Physiological and molecular characteristics associated with the anti-senescence in Camellia oleifera Abel.

“…Our results indicate that the contents of MDA and H2O2 in leaves of C. oleifera increased with the increase of tree age, which was similar to other studies (Turfan et al 2020). However, the activity of SOD, POD, and CAT antioxidant enzymes in the ancient C. oleifera leaves was significantly higher, similar to the report of Chang et al (2019). Antioxidant enzymes are critical in the suppression of aging (Liu et al 2022), CAT and POD are specific enzymes that remove H2O2, and SOD mainly scavenges superoxide anion radicals.…”

“…These theories also indicate that tree senescence is formed under the combined action of many different factors. Meanwhile, due to different mechanisms and inducing factors of senescence (Chang et al 2019), different plants have inconsistent senescence processes. When encountering several external stress and internal senescence-related factors, some plants could form corresponding defense mechanisms through antioxidant enzymes, transcription factors, and signal transduction pathways to prolong their senescence process.…”

“…Leaf senescence was closely related to plant senescence (Lim et al 2007). Regarding leaf aging, anatomy, ultrastructure, photosynthetic efficiencies, chemical components, and the expression of agingrelated genes were studied in Platycladus, Ginkgo biloba, and other tree species (Chang et al 2019, Liu et al 2019, Turfan et al 2020, Wang et al 2020, Yan et al 2021. However, research about C. oleifera trees in anti-senescence is scarce.…”

Genetic Evaluation of Ancient Platycladus orientalis L. (Cupressaceae) in the Middle Reaches of the Yellow River Using Nuclear Microsatellite Markers

“…Previous studies on ancient P. orientalis have mainly focused on revealing its longevity mechanism [26,27] and mapping the climatically suitable habitat of P. orientalis for introduction and cultivation on a global scale [28,29]. Zhu et al [9,30] used nine SSR loci to analyze the genetic diversity of 94 300-year-old P. orientalis individuals growing near ancient temples or cemeteries in Beijing and confirmed that ancient P. orientalis played an important role in maintaining the genetic diversity and reproductive ability of the tree species.…”

“…Zhu et al [9,30] used nine SSR loci to analyze the genetic diversity of 94 300-year-old P. orientalis individuals growing near ancient temples or cemeteries in Beijing and confirmed that ancient P. orientalis played an important role in maintaining the genetic diversity and reproductive ability of the tree species. Chang et al [26] used the specific-locus amplified fragment (SLAF)-specific locus sequencing method to detect SNPs in the genomes of 100 individuals that were obtained from 13 ancient P. orientalis populations in China. The results suggested that the relationships among many individuals were inconsistent with their geographical locations.…”