Integrated Cytological, Physiological, and Transcriptome Analyses Provide Insight into the Albino Phenotype of Chinese Plum (Prunus salicina).

Albino seedlings that arise during seed reproduction can have a significant impact on plant growth and breeding. In this research, we present the first report of albino occurrences in the seed reproduction process of Prunus salicina and describe the cytological, physiological, and transcriptomic changes observed in albino seedlings. The albino seedlings which were observed in several plum cultivars exhibited abnormal chloroplast ultrastructure and perturbed stomatal structure. Compared to normal seedlings, the photosynthetic pigment contents in albino seedlings decreased by more than 90%, accompanied by significant reductions in several chlorophyll fluorescence parameters. Furthermore, substantially changed photosynthetic parameters indicated that the photosynthetic capacity and stomatal function were impaired in albino seedlings. Additionally, the activities of the antioxidant enzyme were drastically altered against the background of higher proline and lower ascorbic acid in leaves of albino seedlings. A total of 4048 differentially expressed genes (DEGs) were identified through transcriptomic sequencing, and the downregulated DEGs in albino seedlings were greatly enriched in the pathways for photosynthetic antenna proteins and flavonoid biosynthesis. GLK1 and Ftsz were identified as candidate genes responsible for the impaired chloroplast development and division in albino seedlings. Additionally, the substantial decline in the expression levels of examined photosystem-related chloroplast genes was validated in albino seedlings. Our findings shed light on the intricate physiological and molecular mechanisms driving albino plum seedling manifestation, which will contribute to improving the reproductive and breeding efforts of plums.

Selection and validation of reference genes for qRT-PCR analysis during fruit ripening of red pitaya (Hylocereus polyrhizus).

Red pitaya (Hylocereus polyrhizus) is widely cultivated in southern and southwestern China. To provide a basis for studying the molecular mechanisms of the ripening of this fruit, we carried out RNA sequencing (RNA-seq) analysis to identify differentially and stably expressed unigenes. The latter may serve as a resource of potential reference genes for normalization of target gene expression determined using quantitative real-time PCR (qRT-PCR). We selected 11 candidate reference genes from our RNA-seq analysis of red pitaya fruit ripening (ACT7, EF-1α, IF-4α, PTBP, PP2A, EF2, Hsp70, GAPDH, DNAJ, TUB and CYP), as well as ß-ACT, which has been used as a reference gene for pitayas in previous studies. We then comprehensively evaluated their expression stability during fruit ripening using four statistical methods (GeNorm, NormFinder, BestKeeper and DeltaCt) and merged the four outputs using the online tool RefFinder for the final ranking. We report that PTBP and DNAJ showed the most stable expression patterns, whereas CYP and ACT7 showed the least stable expression patterns. The relative gene expression of red pitaya sucrose synthase and 4, 5-dihydroxyphenylalanine-extradiol-dioxygenase as determined by quantitative real-time PCR and normalized to PTBP and DNAJ was consistent with the RNA-seq results, suggesting that PTBP and DNAJ are suitable reference genes for studies of red pitaya fruit ripening.

Complete genome sequence of a new member of the genus Badnavirus from red pitaya (Hylocereus polyrhizus).

Here, we report a circular double-stranded DNA virus from red pitaya (Hylocereus polyrhizus). The complete genome sequence is 7,837 nt in length and shares 98.7% nucleotide sequence identity with epiphyllum mottle-associated virus (EpMoaV) and 40.4-54.6% with other members of the genus Badnavirus. It has four open reading frames (ORFs), encoding putative proteins of 19.9, 14.8, 225.7 and 14.2 kDa, respectively. The reverse transcriptase (RT)-ribonuclease H (RNase H) region exhibits less than 70.5% nucleotide sequence identity to RT-RNase H of other badnaviruses, and 99.7% to that of EpMoaV. Phylogenetic analysis revealed that the virus from this study and EpMoaV form a single group. Consequently, we propose this virus as a new member of the genus Badnavirus in the family Caulimoviridae and have named it "pitaya badnavirus 1" (PiBV1). PiBV1 and EpMoaV should be considered two isolates of a badnavirus that infects members of the family Cactaceae.