Transcriptomic and Hormonal Analyses Reveal that YUC-Mediated Auxin Biogenesis Is Involved in Shoot Regeneration from Rhizome in Cymbidium

Abstract

Cymbidium, one of the most important orchid genera in horticulture, can be classified into epiphytic and terrestrial species. Generally, epiphytic Cymbidium seedlings can be easily propagated by tissue culture, but terrestrial seedlings are difficult to propagate. To date, the molecular mechanisms underlying the differences in the ease with which terrestrial and epiphytic cymbidiums can be propagated are largely unknown. Using RNA-sequencing, quantitative reverse transcription PCR and enzyme-linked immunosorbent assay, Cymbidium ‘Xiaofeng’ (CXF), which can be efficiently micropropagated, and terrestrial Cymbidium sinense ‘Qijianbaimo’ (CSQ), which has a low regeneration ability, were used to explore the molecular mechanisms underlying the micropropagation ability of Cymbidium species. To this end, 447 million clean short reads were generated, and 31,264 annotated unigenes were obtained from 10 cDNA libraries. A total of 1,290 differentially expressed genes (DEGs) were identified between CXF and CSQ during shoot induction. Gene ontology (GO) enrichment analysis indicated that the DEGs were significantly enriched in auxin pathway-related GO terms. Further analysis demonstrated that YUC and GH3 family genes, which play crucial roles in the regulation of auxin/IAA (indole-3-acetic acid) metabolism, acted quickly in response to shoot induction culture in vitro and were closely correlated with variation in shoot regeneration between CXF and CSQ. In addition, the study showed that IAA accumulated rapidly and significantly during shoot induction in CXF compared to that in CSQ; in contrast, no significant changes in other hormones were observed between CXF and CSQ. Furthermore, shoot regeneration in CXF was inhibited by a yucasin-auxin biosynthesis inhibitor, indicating that increased IAA level is required for high-frequency shoot regeneration in CXF. In conclusion, our study revealed that YUC-mediated auxin biogenesis is involved in shoot regeneration from rhizome in Cymbidium.

Enhancement of shoot regeneration by treatment with inhibitors of auxin biosynthesis and transport during callus induction in tissue culture of <i>Arabidopsis thaliana</i>

“…The effects of auxin biosynthesis and transport inhibitors on shoot regeneration have been examined in various tissue culture systems. These inhibitors were shown to affect shoot regeneration negatively in some experimental conditions (Cassells 1979;Christianson and Warnick 1984;Dhaliwal et al 2004;Kim and Ernst 1994;Koike et al 2020;Liu et al 2017) and positively in others (Belaizi et al 1991;Bhau and Wakhlu 2001;Cambecèdes et al 1991;Pal et al 2012;Shukla et al 2014;van Aartrijk and Blom-Barnhoorn 1984;Zhang et al 2008). Most of the positive effects were observed in one-step cultures, in which shoot regeneration is induced directly on a cytokinin-rich medium without a preliminary callusinducing culture (Belaizi et al 1991;Cambecèdes et al 1991;Pal et al 2012;Shukla et al 2014; van Aartrijk and Blom-Barnhoorn 1984), whereas, in a few cases, auxin transport inhibitors could increase the number of regenerated shoots when added to SIM in the two-step culture (Bhau and Wakhlu 2001;Zhang et al 2008).…”

MicroRNAs and their targeted genes associated with phase changes of stem explants during tissue culture of tea plant

“…Low expression of the miR396, miR166a-3p, miR157d-5p and miR393c-3p , coupled with up-regulated expression of AIP15A , ATHB15 , GST and ATG18b were observed during shoot regeneration, indicating module of miR396 / AIP15A, miR166a-3p / ATHB15, miR157d-5p/GST and miR393c-3p / ATG18b might be responsible for shoot redifferentiation. In Cymbidium , promoted auxin biosynthesis was required for efficient shoot regeneration 54 . AIP15A belongs to the early auxin-responsive SAUR family gene.…”

Melatonin-induced Rhizome Proliferation, Differentiation, and Rooting during Rapid Propagation of Cymbidium goeringii and Cymbidium faberi

“…Cymbidium, one of the most important orchid genera in horticulture, has %52 epiphytic and terrestrial species (Islam et al, 2015;Kumar et al, 2022). The terrestrial seedlings are difficult to propagate compared with epiphytic species (Liu et al, 2017). A few terrestrial Cymbidium species, such as C. goeringii, C. faberi, C. sinense, C. ensifolium, and C. kanran, are widely cultivated for their beautiful and fragrant flowers (Huang et al, 2012).…”