Time-Course Transcriptome and Phytohormonal Analysis of Blue-Light-Induced Adventitious Root Development of Tea Cuttings (Camellia sinensis (L.) Kuntze)

Abstract

C. sinensis is an economically important crop for tea production that experiences increasing demand and good export potential. Therefore, crops need to be expanded, and high-quality planting material is required. Vegetative propagation by cuttings is the prevalent method; therefore, this paper explored its optimization potential modeled on cultivar ‘Jiukengzao’. This study wanted to deeply explore blue-light-induced adventitious root formation and development of tea cuttings, so we conducted short-term (0 h, 8 h, and 16 h) and long-term (30 d, 60 d, and 90 d) time-course analyses on tea cutting seedlings. Short-term, full-length transcriptome analysis showed that the expression of genes related to plant hormone signal transduction and auxin transport was highest at 16 h. Sixteen hours of light was considered as suitable for adventitious root growth and development of tea cuttings. Long-term phytohormone analysis showed that the trend of indole-3-carboxylic acid (ICA) change was: 60 d > 90 d > 30 d. Long-term, full-length transcriptome analysis showed that the gene expression trends in K2, K5, K6, and K8 clusters were: 90 d > 60 d > 30 d, and the opposite was observed in K1, K4, and K11 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that most of the genes in these seven clusters are involved in “plant hormone signal transduction (ko04075)”. This includes auxin early responsive protein AUX/IAA, auxin response factor ARF, auxin-responsive protein SAUR, etc. In addition, genes related to auxin transport and synthesis were identified as PIN1, 3, 4, PILS2, 6, 7, flavin-containing monooxygenase YUC9, and YUC10, and the expression trend of these genes was mostly consistent with the change trend of ICA content. This study further explained the molecular mechanism of blue-light-induced adventitious root formation and development of tea cuttings. It is recommended that blue light can be used to promote the adventitious root growth and development of tea cuttings in practical production.

Insight into regulation of adventitious root formation by arbuscular mycorrhizal fungus and exogenous auxin in tea plant (Camellia sinensis L.) cuttings

“…In this paper, we only found two YUC DEGs (LOC114300015 and LOC114292052) in tea cuttings at S2 stage (Figure 6C; Supplementary Data 3), in which the expression of YUC10 (LOC114292052) induced by AMF inoculation increased about 3 times more than that in the control treatment, indicating that AMF may promote the biosynthesis of auxin in AR which was just formed. Similar results also found in the study of Shen et al (2023) together with another increased YUC gene (YUC9). At stage of S0 and S1, no significant expressions of YUC genes between mycorrhizal treatment and the control showed the less affection of AMF on auxin biosynthesis of tea cuttings.…”

“…These primordia later develop into fully functional adventitious roots. Genes of auxin biosynthesis and metabolism (flavin-containing monooxygenase YUC and acyl acid amido synthetase GH3 , transport (PIN-FORMED protein PIN and PIN-likes PILS ) and signal transduction (auxin early responsive protein AUX/IAA , auxin response factor ARF , and auxin-responsive protein SAUR ) are all closely correlated with the adventitious root formation as showed in many previous studies ( Yin et al., 2020 ; Hu et al., 2023 ; Shen et al., 2023 ; Wei et al., 2023 ; Zhu et al., 2023 ). Moreover, auxin also interacts with other plant hormones such as cytokinin, ethylene and jasmonic acid to jointly regulate the formation of AR.…”

“…Considering the role of auxin in AMF symbiosis, it is speculated that auxin-related pathways may also be involved in the process of AMF promoting adventitious root formation in tea cuttings. In the study of blue light-induced adventitious rooting of tea cuttings ( Shen et al., 2023 ), auxin signaling transduction genes, such as AUX/IAA ( auxin responsive protein ), ARF ( auxin response factor ) and SAUR ( auxin-responsive protein ) responded most rapidly (16 h after treatment). Moreover, genes related to auxin transport ( PIN1 , 3 and 4 ) and biosynthesis ( YUC9 and 10 ) changed with indole-3-carboxylic acid (ICA) content.…”

“…However, the underlying mechanism of AM fungal regulation on AR formation was not well discussed yet. Therefore, in this paper, we aimed to uncover the preliminary mechanism of AMF regulating rooting ability of tea plant cuttings by centering on auxin, which is the most important phytohormone in the development of AR formation according to previous studies ( Hu et al., 2023 ; Shen et al., 2023 ). Moreover, we firstly separated the process of AR development into 4 stages of non-rooting, AR protrusion, AR formation and AR elongation (which can be seen in part of Materials and methods) at the same sampling time in order to clarify the underlying mechanism.…”