Coexpression analysis of a large-scale transcriptome identified a calmodulin-like protein regulating the development of adventitious roots in poplar

Abstract

Poplars are important woody plants, and the ability to form adventitious roots (ARs) is the key factor for their cultivation because most poplars are propagated by cloning. In previous studies, Ca2+ was confirmed to regulate AR formation in poplar. In this study, wild type poplar cuttings grown in 1.0 mM Ca2+ solution showed the best visible performance of AR development. Coexpression analysis of a large-scale RNA-Seq transcriptome was conducted to identify Ca2+-related genes that regulates AR development in poplar. A total of 15 coexpression modules (CMs) were identified and two CMs showed high association with AR development. Functional analysis identified a number of biological pathways, including “oxidation-reduction process”, “response to biotic stimulus” and “metabolic process”, in tissues of AR development. The Ca2+-related pathway was specifically selected, and its regulation in poplar AR development was predicted. A Ca2+ sensor, PdeCML23–1, which is a member of the calmodulin-like protein (CML) family, was found to promote AR development by phenotypic assay of overexpressed PdeCML23–1 transgenic lines at various growing conditions. By measuring cytosolic Ca2+ in AR tips, PdeCML23–1 seemed to play a role in decreasing cytosolic Ca2+ concentration. Additionally, the expression profiles of some genes and phytohormone IAA were also changed in the overexpressed PdeCML23–1 transgenic lines. According to this study, we were able to provide a global view of gene regulation for poplar AR development. Moreover, we also observed the regulation of cytosolic Ca2+ concentration by PdeCML23–1, and this regulation were involved in AR development in poplar. We also predicted that PdeCML23–1 possibly regulates AR development by modulating IAA content in poplar.

Transcriptomic and Metabolic Analysis of Fruit Development and Identification of Genes Involved in Raffinose and Hydrolysable Tannin Biosynthesis in Walnuts

“…By combining transcriptomic and metabolic data analyses, genes for some metabolite biosynthesis pathways could be identified. The mechanism for the prediction is based on metabolite accumulation correlating with the expression of the corresponding gene, and this mechanism has been tested in a number of previous reports, such as coexpression analyses in poplar and Arabidopsis. − In this study, we mainly focused on biosynthesis pathways for fatty acids, raffinose, and HTs. Four, 3, and 12 genes were predicted to be involved in the biosynthesis of these metabolites, respectively.…”

“…The detailed procedures for A. rhizogenes strain K599 transformation are similar to those of previous studies in which poplar was transformed with Agrobacterium. tumefaciens. , Leaf explants of poplar cv. “Shanxinyang” were inoculated with a suspension of K599 strains harboring expressed SDH , UGT genes, or the empty 2301S plasmid.…”

Adventitious Rooting in Populus Species: Update and Perspectives

“…In the absence of Ca in the media, only 55% of cuttings from the hybrid aspen P. tremula × P. tremuloides developed ARs and the addition of LaCl 3 , a calcium channel blocker, completely inhibited rooting in these cuttings (Bellamine et al, 1998). Recently, Xiao et al (2020) showed that poplar cuttings grown FIGURE 2 | Factors affecting adventitious root formation in Populus. The genotype the mother plant will have an effect on the ability of the cutting to root.…”

“…In the absence of Ca in the media, only 55% of cuttings from the hybrid aspen P. tremula × P. tremuloides developed ARs and the addition of LaCl 3 , a calcium channel blocker, completely inhibited rooting in these cuttings ( Bellamine et al, 1998 ). Recently, Xiao et al (2020) showed that poplar cuttings grown on hydroponic solutions added with 1 mM of Cl 2 Ca significantly increased the AR length and fresh weight, whereas 6 mM had the opposite effect. These results confirm that Ca regulate late phases of AR formation in Populus .…”

Molecular Bases for the Regulation of Adventitious Root Generation in Plants

“…Calmodulin is involved in AR formation by modulating IAA content. A recent study showed that the poplar transgenic lines with overexpressed the calmodulin-like protein (CML) family gene, PdeCML23-1, exhibited more ARs and higher IAA accumulation in cuttings (Xiao et al, 2020). Auxin receptor genes have also been demonstrated to be involved in AR formation.…”