Search

Auxin response factor (ARF) acts as a vital component of auxin signaling and participates in growth, development, and stress responses in plants. In the present study, we comprehensively analyzed kiwifruit’s (Actinidia chinensis) ARF genes (AcARFs) and their involvement in abiotic stress response. We identified a total of 41 AcARFs encoding ARFs in the A. chinensis genome. AcARF genes were characterized by the classic ARF_resp and a B3 domain and primarily localized on the cytoplasm and nucleus. AcARFs were categorized into eight subgroups as per the phylogenetic analysis. Synteny analysis showed that 35 gene pairs in AcARF family underwent segmental and whole genome duplication events. Promoter cis-element prediction revealed that AcARFs might be involved in abiotic factors related to stress response, which was later assessed and validated by qRT-PCR based expression analysis. Additionally, AcARFs showed tissue-specific expression. These findings extend our understanding of the functional roles of AcARFs in stress responses. Taken together, the systematic annotation of the AcARF family genes provides a platform for the functional and evolutionary study, which might help in elucidating the precise roles of the AcARFs in stress responses.

The aroma chemical composition of commonly planted kiwifruit cultivars in China was analyzed. The combination of 2-octanone with 3-octanone was the most suitable dual internal standard for quantitative analysis in GC-MS. A total of 172 aroma components in 23 kiwifruit cultivars were detected, and ethyl butanoate, (E)-2-hexen-1-ol, and (E)-2-hexenal could be considered the core aroma components in kiwifruit, but still need further confirmation using Sensomics. E-nose could effectively distinguish different cultivars of kiwifruit. Clustering based on GC-MS and E-nose results tends to be consistent and demonstrate a certain degree of similarity. Kiwifruit cultivars with different flesh colors cannot be effectively distinguished by their aroma chemical compositions. Different species of kiwifruit can be distinguished to some extent by their aroma chemical compositions, but the effect was not satisfactory. These results could prove valuable in the breeding, planting, and marketing of kiwifruits.

Auxin response factor (ARF) acts as a vital component of auxin signaling and participates in growth, development, and stress responses in plants. In the present study, we comprehensively analyzed kiwifruit’s (Actinidia chinensis) ARF genes (AcARFs) and their involvement in abiotic stress response. We identified a total of 41 AcARFs encoding ARFs in the A. chinensis genome. AcARF genes were characterized by the classic ARF_resp and a B3 domain and primarily localized on the cytoplasm and nucleus. AcARFs were categorized into eight subgroups as per the phylogenetic analysis. Synteny analysis showed that 35 gene pairs in AcARF family underwent segmental and whole genome duplication events. Promoter cis-element prediction revealed that AcARFs might be involved in abiotic factors related to stress response, which was later assessed and validated by qRT-PCR based expression analysis. Additionally, AcARFs showed tissue-specific expression. These findings extend our understanding of the functional roles of AcARFs in stress responses. Taken together, the systematic annotation of the AcARF family genes provides a platform for the functional and evolutionary study, which might help in elucidating the precise roles of the AcARFs in stress responses. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01011-4.

The nutritional quality and antioxidant capacity of China domestic kiwifruit and imported kiwifruit with different prices and the relationships of retail price among cultivars, nutritional qualities and flesh color were investigated. Results showed that cultivar was the main factor influencing nutritional quality, though the product region could also affect the cultivar characteristics to some extent. Additionally, nutritional quality and antioxidant capacity of kiwifruit had no relationship to the product region. What's more, there was no correlation among the nutrient compositions, antioxidant capacity and retail price of kiwifruit. At the same time, the flesh color was associated with greater commercial value but was not higher nutritional quality or antioxidant capacity. Thus indicates to consumers that imported kiwifruit were not all superior to local versions, and the priciest kiwifruit did not equal to the most nutritious kiwifruit, also the color kiwifruit. There still need more research to help consumers to choose kiwifruit.

This study investigated the effects of planting ages on microbial biomass and community diversity in kiwifruit orchard soils through cultured-based microorganism, microbial biomass and Biologanalyses. Our results showed that: (1) Counting of soil cultivable microorganism showed that the amountof bacteria increased firstly and then decreased with the increasing of planting age. The amount of fungi increased after planting kiwifruit and made the soil fungous. However, actinomyces did not change obviously. (2) Microbial biomasses C and N both increased at first, and then decreased obviously with planting ages. (3) Biolog analyses showed that there were significant differences in carbon utilization and soil microbial community functional diversities among kiwifruit orchard and wasteland soils. AWCD, Shannon index, Simpson index and McIntosh index were highest in five aged and lowest in eleven aged kiwifruit orchard soils. Relative utilization value of carbon sources showed that soil microbial communities tended more conducive to using carbohydrate and amino acids and less conducive to using polyphenols and polyamines with planting ages. The principal component analyses showed that there were significant differences in carbon utilizations. Significantly differences in PC1 were found among different aged kiwifruit orchard soils and the differences were mostly caused by carbohydrate, amino acids and polymers, which affecting soil microbial community under kiwifruit planting mostly. Nevertheless, uncultivated and cultivated kiwifruit soils were separated in PC2. We concluded that soil microbial biomass reduced and microbial community diversities decreased under long-term kiwifruit planting, and this might be the main reason that kiwifruit yield decrease and quality decline.

Kiwifruit plants are rich in ascorbic acid (AsA), but AsA production varies widely among species within the Actinidia genus. During AsA synthesis, GDP- l -galactose phosphorylase (GGP: EC 2.7.7.69) catalyzes the conversion of GDP- l -galactose to l -galactose-1-P in the first committed step of the Smirnoff–Wheeler pathway. We noted some correlation between relative levels of GGP mRNA and AsA concentrations in two species during early fruit development. Transcripts were more abundant in Actinidia eriantha than in A. rufa. Furthermore, GUS activity of the entire AeGGP promoter was greater than those in ArGGP promoter under normal growing conditions. Results from our promoter deletion analysis suggest that some negative cis-elements exist in the ArGGP promoter, decreasing the transcriptional levels of GGP in A. rufa. Moreover, the proximal 152 bp from the transcription initiation site is necessary for establishing constitutive expression of that promoter. Thus, we speculated that the GGP promoter may have an important role in regulating GGP transcription, therefore affecting AsA contents in kiwifruit.

Myo -inositol (MI) is an important polyol involved in cellular signal transduction, auxin storage, osmotic regulation, and membrane formation. It also serves as a precursor for the production of pinitol, ascorbic acid, and members of the raffinose family. The first committed step for MI formation is catalyzed by L- myo -inositol-1-phosphate synthase (MIPS). We isolated MIPS cDNA sequences from Actinidia eriantha , Actinidia rufa , and Actinidia arguta and compared them with that of Actinidia deliciosa . Each comprised 1533 bp, encoding 510 amino acids with a predicted molecular weight of 56.5 KDa. The MIPS protein was highly conserved in Actinidia , sharing 98.94% identity among species. The MIPS gene was expressed in the flowers, leaves, petioles, and carpopodia. Similarly high levels of expression were detected in the young fruit of all four species. Overall activity of the enzyme was also maximal in young fruit, indicating that this developmental stage is the key point for MI synthesis in Actinidia . Among the four species, A. arguta had the greatest concentration of MI as well as the highest ratios of MI:sucrose and MI:glucose + fructose. This suggests that conversion to MI from carbohydrates was most efficient in A. arguta during early fruit development.