Molecular and biochemical analyses of avocado (Persea americana) reveal differences in the oil accumulation pattern between the mesocarp and seed during the fruit developmental period

Abstract

Background: The avocado (Persea americana) mesocarp and seed contain high-value oil with broad industrial applications. The oil contents in these two tissues vary considerably at maturity. Additionally, the molecular mechanism underlying the tissue-specific oil accumulation in the developing avocado mesocarp and seed remains unclear, which has hampered the exploration of the utility of avocado for oil production. Results: To clarify the mechanisms mediating the differences in oil contents and fatty acid compositions, the transcriptomes and oil bodies were compared between the oil-storing tissues during the fruit developmental period. The results revealed the increasing and fluctuating trends in the oil accumulation in the developing avocado mesocarp and seed, respectively. Additionally, striking differences in the lipid droplets between the mature mesocarp and seed were revealed in confocal microscopy images. Subsequently, the gene transcription profiles of the developing mesocarp and seed were characterized via a comprehensive transcriptome analysis involving second-generation sequencing and single-molecule real-time sequencing techniques. The tissue-specific transcription of lipid-related genes contributing to fatty acid synthesis, triacylglycerol assembly, and triacylglycerol storage was examined, with most of the lipid-related genes expressed at higher levels in the developing mesocarp than in the developing seed. A weighted gene co-expression network analysis uncovered 291 transcription factors that were commonly or uniquely correlated with the oil contents in the avocado mesocarp and seed. Moreover, 11 transacting and 79 cis-acting long non-coding RNAs were identified as common or unique to the developing avocado mesocarp and seed. These long noncoding RNAs may regulate the expression of 43 lipid-related genes. Finally, a network of genes associated with oil accumulation in the developing avocado mesocarp and seed was established. Conclusions: The results of this study further elucidate the tissue-specific oil biosynthesis and related regulatory network in the avocado mesocarp and seed. Furthermore, tissue-specific lipidrelated genes, putative transcription factors, and putativelong non-coding RNAs affecting oil accumulation were identified. Our data may also be useful for characterizing tissue-specific oil accumulation at the transcriptomic level, thereby identifying candidate genes for improving the oil

Transcriptomic Analysis Reveals Key Genes Involved in Oil and Linoleic Acid Biosynthesis during Artemisia sphaerocephala Seed Development

“…The key TFs that regulated the biosynthesis of oil varied by species and different organizations: GRF5, WRI1, FUS3 were hub TFs in the oil biosynthesis regulatory network in B. rape seed [39]. WRI1, MYB and ZIP played key roles in the biosynthesis of oil in C. oleifera [40]; PBS and RAP played a critical role in the oil biosynthesis regulatory network in avocado (Persea americana) mesocarp and seed, respectively [41]. For this study, a total of 1440 differentially expressed TFs belonging to 83 different gene families were identified from the seed transcriptome of A. sphaerocephala at different developmental stages.…”

24-Epibrassinolide Promotes Fatty Acid Accumulation and the Expression of Related Genes in Styrax tonkinensis Seeds

“…Transcription factors (TFs) operate in gene regulatory networks by controlling the expression of crucial genes coding for some enzymes involved in FA biosynthesis in plant seeds [ 44 ]. GRF5 , WRI1 , and FUS3 played a role in the oil biosynthesis regulatory network in Brassica rape seeds [ 45 ], however, PBS and RAP were primary TFs in oil biosynthesis in Persea americana seeds [ 46 ]. As described in Figure 11 , MYB (213), C2H2 (141), AP2/ERF (130), bHLH (108), GRAS (106), bZIP (99), C2C2 (94), and WRKY (75) dominated in the FA biosynthesis of S. tonkinensis seeds.…”

Multi-Omics Analysis to Visualize Ecotype-Specific Heterogeneity of the Metabolites in the Mesocarp Tissue of Three Avocado (Persea Americana Mill.) Ecotypes

“…The mesocarps of ten avocado fruits were combined to form one biological replicate and homogenized using a high-speed homogenizer for the subsequent extraction of fatty acids. The fatty acid compositions were determined using the GC-MS method described by Ge et al [20]. Similarly, qualitative and quantitative analyses of fatty acid compositions were performed according to the method described by Ge et al [20].…”