Physiological and transcriptomic analyses reveal the regulatory mechanisms of Anoectochilus roxburghii in response to high-temperature stress.

BACKGROUND: High temperatures significantly affect the growth, development, and yield of plants. Anoectochilus roxburghii prefers a cool and humid environment, intolerant of high temperatures. It is necessary to enhance the heat tolerance of A. roxburghii and breed heat-tolerant varieties. Therefore, we studied the physiological indexes and transcriptome of A. roxburghii under different times of high-temperature stress treatments. RESULTS: Under high-temperature stress, proline (Pro), H2O2 content increased, then decreased, then increased again, catalase (CAT) activity increased continuously, peroxidase (POD) activity decreased rapidly, then increased, then decreased again, superoxide dismutase (SOD) activity, malondialdehyde (MDA), and soluble sugars (SS) content all decreased, then increased, and chlorophyll and soluble proteins (SP) content increased, then decreased. Transcriptomic investigation indicated that a total of 2740 DEGs were identified and numerous DEGs were notably enriched for "Plant-pathogen interaction" and "Plant hormone signal transduction". We identified a total of 32 genes in these two pathways that may be the key genes for resistance to high-temperature stress in A. roxburghii. CONCLUSIONS: To sum up, the results of this study provide a reference for the molecular regulation of A. roxburghii's tolerance to high temperatures, which is useful for further cultivation of high-temperature-tolerant A. roxburghii varieties.

Genome-Wide Identification and Expression Analysis of the Aux/IAA Gene Family of the Drumstick Tree (Moringa oleifera Lam.) Reveals Regulatory Effects on Shoot Regeneration.

Auxin plays a critical role in organogenesis in plants. The classical auxin signaling pathway holds that auxin initiates downstream signal transduction by degrading Aux/IAA transcription repressors that interact with ARF transcription factors. In this study, 23 MoIAA genes were identified in the drumstick tree genome. All MoIAA genes were located within five subfamilies based on phylogenetic evolution analysis; the gene characteristics and promoter cis-elements were also analyzed. The protein interaction network between the MoIAAs with MoARFs was complex. The MoIAA gene family responded positively to NAA treatment, exhibiting different patterns and degrees, notably for MoIAA1, MoIAA7 and MoIAA13. The three genes expressed and functioned in the nucleus; only the intact encoding protein of MoIAA13 exhibited transcriptional activation activity. The shoot regeneration capacity in the 35S::MoIAA13-OE transgenic line was considerably lower than in the wild type. These results establish a foundation for further research on MoIAA gene function and provide useful information for improved tissue culture efficiency and molecular breeding of M. oleifera.

Global Transcriptomic Analysis Reveals Differentially Expressed Genes Involved in Embryogenic Callus Induction in Drumstick (Moringa oleifera Lam.).

The plant embryogenic callus (EC) is an irregular embryogenic cell mass with strong regenerative ability that can be used for propagation and genetic transformation. However, difficulties with EC induction have hindered the breeding of drumstick, a tree with diverse potential commercial uses. In this study, three drumstick EC cDNA libraries were sequenced using an Illumina NovaSeq 6000 system. A total of 7191 differentially expressed genes (DEGs) for embryogenic callus development were identified, of which 2325 were mapped to the KEGG database, with the categories of plant hormone signal transduction and Plant-pathogen interaction being well-represented. The results obtained suggest that auxin and cytokinin metabolism and several embryogenesis-labeled genes are involved in embryogenic callus induction. Additionally, 589 transcription factors from 20 different families were differentially expressed during EC formation. The differential expression of 16 unigenes related to auxin signaling pathways was validated experimentally by quantitative real time PCR (qRT-PCR) using samples representing three sequential developmental stages of drumstick EC, supporting their apparent involvement in drumstick EC formation. Our study provides valuable information about the molecular mechanism of EC formation and has revealed new genes involved in this process.