Considering that Actinidia kolomikta bears abundant white leaves on reproductive branches during blossoming, we hypothesized that the white leaves may maintain photosynthetic capacity by adjustments of leaf anatomy and physiological regulation. To test this hypothesis, leaf anatomy, gas exchange, chlorophyll a fluorescence, and the transcriptome were examined in white leaves of A. kolomikta during flowering. The palisade and spongy mesophyll in the white leaves were thicker than those in green ones. Chloroplast development in palisade parenchyma of white leaves was abnormal, whereas spongy parenchyma of white leaves contained functional chloroplasts. The highest photosynthetic rate of white leaves was ~82% of that of green leaves over the course of the day. In addition, the maximum quantum yield of PSII (F_v/F_m) of the palisade mesophyll in white leaves was significantly lower than those of green ones, whereas F_v/F_m and quantum yield for electron transport were significantly higher in the spongy mesophyll of white leaves. Photosynthetic capacity regulation of white leaf also was attributed to upregulation or downregulation of some key genes involving in photosynthesis. Particularly, upregulation of sucrose phosphate synthase (SPS), glyeraldehyde-3-phosphate dehydrogenase (GAPDH) and RuBisCO activase (RCA) in white leaf suggested that they might be involved in regulation of sugar synthesis and Rubisco activase in maintaining photosynthetic capacity of white leaf. Conclusions: white leaves contained a thicker mesophyll layer and higher photosynthetic activity in spongy parenchyma cells than those of palisade parenchyma cells. This may compensate for the lowered photosynthetic capacity of the palisade mesophyll. Consequently, white leaves maintain a relatively high photosynthetic capacity in the field.

Sugar was transported from photosynthetic source cells to sink cells, sugar efflux transporter protein (sugars will eventually be exported to transporters, SWEETs) play an important role in the process. Although SWEET family members had been identified in many plants, transcriptome or genomics analysis of Actinidia polygama SWEET genes remains uncharacterized. In this study, 14 SWEET genes of Actinidia polygama were identified by protein Blast. The structural characteristics of SWEET genes showed that the number of amino acids encoded by the gene family was between 233 and 304, the relative molecular weight was between 25,918.83 and 33,192.12, the isoelectric point was within the range of 6.96 to 9.71, 14 ApSWEET from Actinidia polygama and the known grape and Arabidopsis SWEETs were divided into four clades (I, II, III, and IV) according to the phylogenetic relationships. The gene structure analysis showed that most of ApSWEET genes have six exons and five introns except ApSWEET5 and ApSWEET14. All ApSWEET proteins also contained P-loop, MtN3-slv, and transmembrane domain. Expression patterns of 14 ApSWEET in different organs and at different fruit developmental stages were analyzed. ApSWEET1 and ApSWEET5 exhibited tissue-specific expression, whereas other genes were more ubiquitously expressed. ApSWEET1, ApSWEET10, and ApSWEET11 exhibited higher expression in fruit. The results of this study provide insights into the characteristics of the SWEET genes in Actinidia polygama and may serve as a basis for further functional studies of such genes.

Schisandra chinensis (Turcz.) Baill. is an important medicinal plant in northeast China. Cutting propagation is an effective method for the rapid propagation of many tree species. This research aimed to determine a suitable growing medium and appropriate root hormone type, concentration and treatment time through the utilization of different substrates and hormones to treat one-year-old branches of S. chinensis. The optimal treatment achieved a rooting rate of 60% with 225 ppm ABT and 75 ppm NAA for 2.5 h. The substrate of vermiculite/perlite = 1:1 (urea+potassium) was beneficial to the adventitious root formation, which reached 79%. The adventitious root primordium of S. chinensis originated from the junction of the xylem and cambium. ABT and NAA treatments altered the peak timing of POD, PPO and IAAO in S. chinensis cuttings. During the adventitious root formation of S. chinensis cuttings, the high endogenous IAA concentration promoted the occurrence of adventitious roots in the early stage and the lower endogenous IAA and GA₃ concentrations promoted the elongation and growth of adventitious roots in the later period. Low ABA and ZR concentrations enabled adventitious root formation and elongation. An efficient cutting propagation system would enable the mass propagation of S. chinensis seedlings.

The sugars will eventually be exported transporter (SWEET) family is a novel class of sugar transporters that play a crucial role in plant growth, development, and responses to stress. Cranberry (Vaccinium macrocarpon Ait.) is a nutritious berry with economic importance, but little is known about SWEET gene family functions in this small fruit. In this research, 13 VmSWEET genes belonging to four clades were identified in the cranberry genome for the first time. In the conserved domains, we observed seven phosphorylation sites and four amino acid residues that might be crucial for the binding function. The majority of VmSWEET genes in each clade shared similar gene structures and conserved motifs, showing that the VmSWEET genes were highly conserved during evolution. Chromosomal localization and duplication analyses showed that VmSWEET genes were unevenly distributed in eight chromosomes and two pairs of them displayed synteny. A total of 79 cis-acting elements were predicted in the promoter regions of VmSWEETs including elements responsive to plant hormones, light, growth and development and stress responses. qRT-PCR analysis showed that VmSWEET10.1 was highly expressed in flowers, VmSWEET16 was highly expressed in upright and runner stems, and VmSWEET3 was highly expressed in the leaves of both types of stems. In fruit, the expression of VmSWEET14 and VmSWEET16 was highest of all members during the young fruit stage and were downregulated as fruit matured. The expression of VmSWEET4 was higher during later developmental stages than earlier developmental stages. Furthermore, qRT-PCR results revealed a significant up-regulation of VmSWEET10.2, under osmotic, saline, salt-alkali, and aluminum stress conditions, suggesting it has a crucial role in mediating plant responses to various environmental stresses. Overall, these results provide new insights into the characteristics and evolution of VmSWEET genes. Moreover, the candidate VmSWEET genes involved in the growth, development and abiotic stress responses can be used for molecular breeding to improve cranberry fruit quality and abiotic stress resistance.

Hardy kiwifruit (Actinidia arguta) is a promising fruit species in the family Actinidiaceae with increasing commercial production worldwide (Latocha et al. 2014). During April and May of 2015, with high humidity and cool temperature conditions, typical symptoms of Sclerotinia rot with about 10% incidence were observed on 2-year-old seedlings in Zuojia Town, Jilin Province, China. Symptoms started as black-brown watery soft rot, quickly expanded and girdled on the basal stems, at the same time the leaves became yellow and wilted. Finally, the plants wilted and died. White mycelium and occasionally irregular black sclerotia (1.2 to 4.5 mm in diameter) were also observed on the rotted basal stem and roots of plants. Sclerotia were collected from symptomatic tissue, surface-disinfested with 70% ethanol for 30 sec and 0.1% HgCl2 for 1 min, triple rinsed with sterile water, and plated on potato dextrose agar (PDA), and incubated 4 to 5 days at 20 °C. Within 2 to 4 days, white mycelia were pulled from the sclero...

Actinidia arguta is a cold-resistant fruit tree but intolerant to waterlogging. Waterlogging stress is the major abiotic stress in A. arguta growth, and several pathways are involved in the response mechanisms. Fifteen physiological indices and transcriptome data of two A. arguta cultivars, which showed two forms under waterlogging, were used to identify the major factor following the leaf senescence in waterlogging. Through principal component analysis (PCA) of 15 physiological indices in ‘Kuilv’ and ‘Lvwang’, the hormone contents were selected as the most important principal component (PCA 2) out of four components in response to waterlogging stress. According to the analysis of transcriptome data, 21,750 differentially expressed genes were identified and 10 genes through WGCNA, including hormone metabolism and sucrose metabolism, were screened out on the 6th day of waterlogging. In particular, the ABA signal transduction pathway was found to be closely related to the response to waterlogging based on the correlation analysis between gene expression level and plant hormone content, which may have regulated physiological indicators and morphological changes together with other hormones. Overall, the phenomenon of leaves falling induced by ABA might be a protective mechanism. The results provided more insights into the response mechanism of coping with waterlogging stress in A. arguta.