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.

Chromosome-level draft genome of a diploid plum (Prunus salicina).

BACKGROUND: Plums are one of the most economically important Rosaceae fruit crops and comprise dozens of species distributed across the world. Until now, only limited genomic information has been available for the genetic studies and breeding programs of plums. Prunus salicina, an important diploid plum species, plays a predominant role in modern commercial plum production. Here we selected P. salicina for whole-genome sequencing and present a chromosome-level genome assembly through the combination of Pacific Biosciences sequencing, Illumina sequencing, and Hi-C technology. FINDINGS: The assembly had a total size of 284.2 Mb, with contig N50 of 1.78 Mb and scaffold N50 of 32.32 Mb. A total of 96.56% of the assembled sequences were anchored onto 8 pseudochromosomes, and 24,448 protein-coding genes were identified. Phylogenetic analysis showed that P. salicina had a close relationship with Prunus mume and Prunus armeniaca, with P. salicina diverging from their common ancestor ∼9.05 million years ago. During P. salicina evolution 146 gene families were expanded, and some cell wall-related GO terms were significantly enriched. It was noteworthy that members of the DUF579 family, a new class involved in xylan biosynthesis, were significantly expanded in P. salicina, which provided new insight into the xylan metabolism in plums. CONCLUSIONS: We constructed the first high-quality chromosome-level plum genome using Pacific Biosciences, Illumina, and Hi-C technologies. This work provides a valuable resource for facilitating plum breeding programs and studying the genetic diversity mechanisms of plums and Prunus species.