Transcriptomic analysis of interstockinduced dwarfism in Sweet Persimmon(Diospyros kaki Thunb.)

Growth monitoring indicated that the height of‘Kanshu’plants with‘Nantong-xiaofangshi’as an interstock was significantly shorter than that of‘Kanshu’plants with no interstock.A transcriptome analysis of the two graft combinations(‘Kanshu’/Diospyros lotus and‘Kanshu’/‘Nantong-xiaofangshi’/Diospyros lotus)was conducted to explore the dwarfing genes related to the use of the‘Nantong-xiaofangshi’interstock.Hormone levels and water conductance were also measured in these two graft combinations.The results indicated that the levels of both IAA and GA were lower in‘Kanshu’that had been grafted onto the‘Nantong-xiaofangshi’interstock than in‘Kanshu’with no interstock;additionally,the water conductance was lower in grafts with interstocks than in grafts without interstocks.The expression of AUX/IAA and auxin-responsive GH3 genes was enhanced in scions grafted on the interstock and was negatively correlated with the IAA content and growth of scions.The expression of GA2ox,DELLA,and SPINDLY genes were also upregulated and associated with a decrease in the level of GA in scions grafted on the interstock.Since one of the GA2ox unigenes was annotated as DkGA2ox1 in Diospyros kaki,but was not functionally validated,a functional analysis was conducted in transgenic tobacco.Overexpression of DkGA2ox1 in transgenic plants resulted in a dwarf phenotype that could be recovered by the exogenous application of GA3.We conclude that the‘Nantong-xiaofangshi’interstock affects the water conductance and expression of genes related to the metabolism and transduction of IAA and GA in the grafted scion and thus regulates phytohormone levels,producing dwarfing.

Metabolic changes upon flower bud break in Japanese apricot are enhanced by exogenous GA_(4)

Gibberellin (GA_(4)) has a significant effect on promoting dormancy release in flower buds of Japanese apricot (Prunus mume Sieb. et Zucc). The transcriptomic and proteomic changes that occur after GA_(4) treatment have been reported previously;however, the metabolic changes brought about by GA_(4) remain unknown. The present study was undertaken to assess changes in metabolites in response to GA_(4) treatment, as determined using gas chromatography–mass spectrometry and principal component analysis. Fifty-five metabolites that exhibited more than two-fold differences in abundance (P < 0.05) between samples collected over time after a given treatment or between samples exposed to different treatments were studied further. These metabolites were categorized into six main groups: amino acids and their isoforms (10), amino acid derivatives (7), sugars and polyols (14), organic acids (12), fatty acids (4), and others (8). All of these groups are involved in various metabolic pathways, in particular galactose metabolism, glyoxylate and dicarboxylate metabolism, and starch and sucrose metabolism. These results suggested that energy metabolism is important at the metabolic level in dormancy release following GA_(4) treatment. We also found that more than 10-fold differences in abundance were observed for many metabolites, including sucrose, proline, linoleic acid, and linolenic acid, which might play important roles during the dormancy process. The current research extends our understanding of the mechanisms involved in budburst and dormancy release in response to GA_(4) and provides a theoretical basis for applying GA_(4) to release dormancy.

MdWRKY75e enhances resistance to Alternaria alternata in Malus domestica

The Alternaria alternata apple pathotype adversely affects apple(Malus domestica Borkh.)cultivation.However,the molecular mechanisms underlying enhanced resistance to this pathogen in apple remain poorly understood.We have previously reported that MdWRKY75 expression is upregulated by A.alternata infection in‘Sushuai’apples.In this study,we discovered that overexpression of MdWRKY75e increased the resistance of transgenic apple lines to A.alternata infection,whereas silencing this gene enhanced susceptibility to A.alternata infection.Furthermore,we found that MdWRKY75e directly binds to the MdLAC7 promoter to regulate the biosynthesis of laccase and increase the biosynthesis of lignin during A.alternata infection.Moreover,the thickening of the cell wall enhanced the mechanical defense capabilities of apple.In addition,we found that jasmonic acid remarkably induced MdWRKY75e expression,and its levels in transgenic apple lines were elevated.These results indicate that MdWRKY75e confers resistance to the A.alternata apple pathotype mainly via the jasmonic acid pathway and that pathogenesis-related genes and antioxidant-related enzyme activity are involved in the disease resistance of MdWRKY75e transgenic plants.In conclusion,our fi ndings provide insights into the importance of MdWRKY75e for resistance to A.alternata infection in apples.