Efficient Micropropagation of Chestnut Hybrids(Castanea spp.)Using Modified Woody Plant Medium and Zeatin Riboside

The chestnuts genus(Castanea spp.)is comprised of economically important trees native to the Northern hemisphere that are used as food and hardwood timber.Here,a very efficient method for micropropagation of European×Japanese chestnut hybrids(Castanea sativa×C.crenata)is described.Woody Plant Medium was used as the basal medium.In vitro shoots of four rootstock cultivars were micropropagated without shoot-tip necrosis on multiplication medium containing 5.7 or 11.4μmol·L^(−1)zeatin riboside,and were rooted on rooting medium containing 2.46μmol·L^(−1)indolebutyric acid.Monthly shootmultiplication rates for each cultivarwere 2–5 folds.In vitro rooting percentages for four cultivars were 87%for‘Maraval’,67%for‘Marigoule’,93%for‘Marsol’,and 97%for‘Précoce Migoule’.Within a 5 week period,80%–95%of rooted shoots were successfully acclimated under high humidity conditions after they were planted in either soil or rockwool.

The plant hormone zeatin riboside inhibits T lymphocyte activity via adenosine A2A receptor activation

Cytokinins are plant hormones that play an integral role in multiple aspects of plant growth and development. The biological functions of cytokinins in mammalian systems are, however, largely uncharacterized. The naturally occurring cytokinin zeatin riboside has recently been demonstrated to activate the mammalian adenosine A2A receptor, which is broadly expressed by various cell types including immune system cells, with the activation of the A2AR playing a role in the regulation of cells involved in both innate and adaptive immunity. We show for the first time that zeatin riboside modulates mammalian immune system activity via an A2AR-dependent mechanism. Specifically, zeatin riboside treatment induces the production of cyclic adenosine monophosphate （cAMP） by T lymphocytes and inhibits the production by CD3^＋CD4^＋ T cells of interferon （IFN）-γ, IL-2, tumor-necrosis factor （TNF）-α, IL-4 and IL-13, and the production by CD3^＋CD8^＋ T cells of IFN-γ, IL-2 and TNF-α. Additionally, the upregulation of CD25, CD69 and CD40L by activated T lymphocytes is modulated by zeatin riboside. Zeatin riboside treatment also potently inhibits thioglycollate-induced peritoneal leukocytosis. The immunomodulatory activities of zeatin riboside are blocked by co-treatment with the selective A2AR antagonist ZM241385. These data suggest that zeatin riboside possesses therapeutic potential as a mammalian immunomodulatory agent.

Characterization of long-term ex vivo expansion of tree shrew spermatogonial stem cells

Tree shrews(Tupaia belangeri chinensis)share a close relationship to primates and have been widely used in biomedical research.We previously established a spermatogonial stem cell(SSC)-based gene editing platform to generate transgenic tree shrews.However,the influences of long-term expansion on tree shrew SSC spermatogenesis potential remain unclear.Here,we examined the in vivo spermatogenesis potential of tree shrew SSCs cultured across different passages.We found that SSCs lost spermatogenesis ability after long-term expansion(>50 passages),as indicated by the failure to colonize the seminiferous epithelium and generate donor spermatogonia(SPG)-derivedspermatocytesor spermatids marking spermatogenesis.RNA sequencing(RNA-seq)analysis of undifferentiated SPGs across different passages revealed significant gene expression changes after sub-culturing primary SPG lines for more than 40 passages on feeder layers.Specifically,DNA damage response and repair genes(e.g.,MRE11,SMC3,BLM,and GEN1)were down-regulated,whereas genes associated with mitochondrial function(e.g.,NDUFA9,NDUFA8,NDUFA13,and NDUFB8)were up-regulated after expansion.The DNA damage accumulation and mitochondrial dysfunction were experimentally validated in high-passage cells.Supplementation with nicotinamide adenine dinucleotide(NAD+)precursor nicotinamide riboside(NR)exhibited beneficial effects by reducing DNA damage accumulation and mitochondrial dysfunction in SPG elicited by long-term culture.Our research presents a comprehensive analysis of the genetic and physiological attributes critical for the sustained expansion of undifferentiated SSCs in tree shrews and proposes an effective strategy for extended in vitro maintenance.

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in Alternate Bearing of Black Pepper (<i>Piper nigrum</i>L.)

Alternate bearing habit, a common phenomenon prevalent in some of the fruit trees is observed in black pepper variety Panniyur-1 also. In this study, an attempt was made to investigate the role of carbohydrates, mineral nutrients and plant hormones (IAA and zeatin riboside) in alternate bearing in Panniyur-1 variety. The experiment was conducted for three consecutive years at Murugarajendra estate, Madikeri, Karnataka, India (12.42。N, 75.73。E). Carbohydrate, mineral nutrient and plant hormone (IAA and zeatin riboside) statuses of the leaves as well as fruiting branches (stem) were compared between good fruiting year (on year) and low fruiting year (off year). Results revealed that concentration of mineral nutrients in leaves was more during on year compared to off year while the reverse was true on the stem. Both stem and leaf metabolite levels at harvest were higher in off year compared to on year suggesting that remobilization of nutrients to the developing berries must have been affected during off year, thus leading to accumulation of more nutrients at harvest in off year compared to on year. Leaf had higher concentration of most of mineral nutrients compared to stem. Spraying of 1% solution of complex fertilizer 19:19:19 (percent N:P:K) three times at an interval of 3 weeks from flower primordial initiation to flowering period enhanced the yield to the extent of around 30% during off year. Auxin to cytokinin ratio was 6.6 and 6.1 in on year and 6.3 and 5.7 in off year at flowering and 3 months after flowering respectively, suggesting that this ratio itself may not play a major role in flowering during on and off years, though the ratio was slightly more during on year. Results of the study indicate that efficient utilization of metabolites and nutrients in on year may render vine weak in the subsequent year coupled with poor remobilization into developing berries, which could make it an off year.

NAD＋ and its precursors in human longevity

Aging is a complex issue due to its nature in progressive physiological and functional decay. As better medicine, technology, and living conditions became accessible to many people, the longevity of human beings increased during the past centuries. Recent research established vital roles for NAD＋ and its precursors in protecting and maintaining the redox homeostasis in cells, which might be applicable therapeutically to prevent cell degeneration. Notably, the contribution of NAD＋ metabolites to lifespan extension in model systems indicates that the potential beneficial effects of NAD＋ precursors. In this mini review, by introducing the background of NAD＋-consuming enzymes in ＂caloric restriction＂, we focus on NAD＋ and its precursors in diet, with further emphasis on its association with health and diseases. We also provide insights in future utilization ofNAD＋ and its precursors as nutrition supplement for lifespan extension.