Prediction of Effector Proteins from Trichoderma longibrachiatum Through Transcriptome Sequencing.

Trichoderma longibrachiatum SMF2 is an important biocontrol strain isolated by our group that can promote plant growth and induce plant disease resistance. To further study its biocontrol mechanism, the effector proteins secreted by T. longibrachiatum SMF2 were analyzed through bioinformatics and transcriptome sequencing. Overall, 478 secretory proteins produced by T. longibrachiatum were identified, of which 272 were upregulated after treatment with plants. Functional annotation showed that 36 secretory proteins were homologous with different groups of effectors from pathogenic microorganisms. Moreover, the quantitative PCR results of six putative effector proteins were consistent with those of transcriptome sequencing. Taken together, these findings indicate that the secretory proteins secreted by T. longibrachiatum SMF2 may act as effectors to facilitate its own growth and colonization or to induce plant immunity response.

A Chromosome-Level Genome Assembly of Garlic (Allium sativum) Provides Insights into Genome Evolution and Allicin Biosynthesis.

Garlic, an economically important vegetable, spice, and medicinal crop, produces highly enlarged bulbs and unique organosulfur compounds. Here, we report a chromosome-level genome assembly for garlic, with a total size of approximately 16.24 Gb, as well as the annotation of 57 561 predicted protein-coding genes, making garlic the first Allium species with a sequenced genome. Analysis of this garlic genome assembly reveals a recent burst of transposable elements, explaining the substantial expansion of the garlic genome. We examined the evolution of certain genes associated with the biosynthesis of allicin and inulin neoseries-type fructans, and provided new insights into the biosynthesis of these two compounds. Furthermore, a large-scale transcriptome was produced to characterize the expression patterns of garlic genes in different tissues and at various growth stages of enlarged bulbs. The reference genome and large-scale transcriptome data generated in this study provide valuable new resources for research on garlic biology and breeding.

Transcriptome Analysis of Low-Temperature-Induced Breaking of Garlic Aerial Bulb Dormancy.

The long history of asexual reproduction of garlic using garlic cloves has resulted in virus accumulation and genetic depression. Propagation of garlic seedlings by tissue culture can both eliminate viruses and improve breeding efficiency. Aerial bulbs are the first-choice materials for breeding virus-free garlic seedlings under external conditions, but they show dormancy just like garlic bulbs. However, low temperatures can quickly break dormancy. In this research, we used a high-throughput sequencing method to sequence aerial bulbs during dormancy and after low-temperature-induced breaking of dormancy to screen out the key differentially expressed genes (DEGs) associated with low temperature and to provide a theoretical basis for exploring the molecular mechanism of low-temperature-induced breaking of aerial bulb dormancy. The high-throughput transcriptome sequencing results showed that 6,675 DEGs were upregulated and 36,596 DEGs were downregulated in the aerial bulbs given low-temperature treatment. Then, 19,507 DEGs were assigned KEGG annotations, among which most DEGs were annotated to the metabolism pathway (11,817 genes, accounting for 60.58%), followed by the genetic information processing pathway (4,521 genes, accounting for 23.18%). The DEGs were mostly concentrated in pathways such as protein processing in the endoplasmic reticulum, plant-pathogen interaction, plant hormone signal transduction, and ribosome biogenesis in eukaryotes, with significant enrichment. The key DEGs related to calcium signaling, hormonal signaling, and transcription factors were screened out, including CaM, CDPK, and CML in accessory pathways of calcium signaling; GA20ox, GAI1, and GA2ox in accessory pathways of hormonal signaling; and transcription factor genes such as MYB, AP2/ERF, bHLH, MADS, and bZIP. qRT-PCR verification results were consistent with the sequencing results, indicating that the transcriptome sequencing data were accurate and reliable. Our results provide a theoretical basis for breaking the dormancy of aerial bulbs with low-temperature treatment to produce virus-free seedlings and increase the output and quality of garlic.