Cloning and Characterization of ThSHRs and ThSCR Transcription Factors in Taxodium Hybrid ‘Zhongshanshan 406’

Abstract

Among the GRAS family of transcription factors, SHORT ROOT (SHR) and SCARECROW (SCR) are key regulators of the formation of root tissues. In this study, we isolated and characterized two genes encoding SHR proteins and one gene encoding an SCR protein: ThSHR1 (Accession Number MF045148), ThSHR2 (Accession Number MF045149) and ThSCR (Accession Number MF045152) in the adventitious roots of Taxodium hybrid ‘Zhongshanshan’. Gene structure analysis indicated that ThSHR1, ThSHR2 and ThSCR are all intron free. Multiple protein sequence alignments showed that each of the corresponding proteins, ThSHR1, ThSHR2 and ThSCR, contained five well-conserved domains: leucine heptad repeat I (LHRI), the VHIID motif, leucine heptad repeat II (LHR II), the PFYRE motif, and the SAW motif. The phylogenetic analysis indicated that ThSCR was positioned in the SCR clade with the SCR proteins from eight other species, while ThSHR1 and ThSHR2 were positioned in the SHR clade with the SHR proteins from six other species. Temporal expression patterns of these genes were profiled during the process of adventitious root development on stem cuttings. Whereas expression of both ThSHR2 and ThSCR increased up to primary root formation before declining, that of ThSHR1 increased steadily throughout adventitious root formation. Subcellular localization studies in transgenic poplar protoplasts revealed that ThSHR1, ThSHR2 and ThSCR were localized in the nucleus. Collectively, these results suggest that the three genes encode Taxodium GRAS family transcription factors, and the findings contribute to improving our understanding of the expression and function of SHR and SCR during adventitious root production, which may then be manipulated to achieve high rates of asexual propagation of valuable tree species.

Identification and functional analysis ofLecRLKgenes inTaxodium‘Zhongshanshan’

“…Taxodium ‘Zhongshanshan’ has been found to show strong adaptability in China, and is now widely used for wetland ecological restoration, coastal shelter forest construction, saline-alkali land afforestation, urban and rural afforestation, and farmland forest networks (Changxiao et al, 2006), offering great landscaping and ecological values. Recently, exploring the stress resistance of Taxodium at the molecular level has become a research focus (Yu, Xu & Yin, 2016; Fan et al, 2018; Wang et al, 2017; Qi et al, 2014). Because of their inability to move, plant can only passively withstand changes in the external environment and various stimuli.…”

Identification and Functional Analysis of ThADH1 and ThADH4 Genes Involved in Tolerance to Waterlogging Stress in Taxodium hybrid ‘Zhongshanshan 406’

“…Hybrid poplar tissue culture seedlings (42-days-old) was grown in tissue culture and protoplasts were released, using cellulase and pectate lyase [ 19 ]. The binary vector p2GWF7.0, harboring the double cauliflower mosaic virus 35S (CaMV35S)-ADH-green fluorescent protein (GFP), was introduced into freshly obtained Populus protoplasts by polyethylene glycol (PEG) and then incubated for 20 h at 23 °C before being observed and recorded.…”

A Perspective on Adventitious Root Formation in Tree Species

“…The expression levels of the GRAS’ SCARECROW and SHORT-ROOT homologs have been associated with adventitious rooting in poplar, Taxodium hybrids, sugi, walnut, chestnut, and pine [ 11 , 15 , 16 , 17 , 41 , 51 , 52 , 53 , 54 , 55 ]. Furthermore, the expression of a specific subset of GRAS family transcription factors is associated with the maturation-related decline of adventitious root formation in both pine and chestnut [ 17 , 52 , 53 , 54 , 55 ].…”