Comparative transcriptome analysis revealed the cooperative regulation of sucrose and IAA on adventitious root formation in lotus (Nelumbo nucifera Gaertn)

Abstract

Background In China, lotus is an important cultivated crop with multiple applications in ornaments, food, and environmental purification. Adventitious roots (ARs), a secondary root is necessary for the uptake of nutrition and water as the lotus principle root is underdeveloped. Therefore, AR formation in seedlings is very important for lotus breeding due to its effect on plant early growth. As lotus ARs formation was significantly affected by sucrose treatment, we analyzed the expression of genes and miRNAs upon treatment with differential concentrations of sucrose, and a crosstalk between sucrose and IAA was also identified. Results Notably, 20 mg/L sucrose promoted the ARs development, whereas 60 mg/L sucrose inhibited the formation of ARs. To investigate the regulatory pathway during ARs formation, the expression of genes and miRNAs was evaluated by high-throughput tag-sequencing. We observed that the expression of 5438, 5184, and 5345 genes was enhanced in the GL20/CK0, GL60/CK0, and CK1/CK0 libraries, respectively. Further, the expression of 73, 78, and 71 miRNAs was upregulated in the ZT20/MCK0, ZT60/MCK0, and MCK1/MCK0 libraries, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that most of the differentially expressed genes and miRNAs in the GL20/GL60 and ZT20/ZT60 libraries were involved in signal transduction. A large number of these genes (29) and miRNAs (53) were associated with plant hormone metabolism. We observed an association between five miRNAs (miR160, miR156a-5p, miR397-5p_1, miR396a and miR167d) and nine genes (auxin response factor, protein brassinosteroid insensitive 1, laccase, and peroxidase 27) in the ZT20/ ZT60 libraries during ARs formation. Quantitative polymerase chain reaction (qRT-PCR) was used to validate the high-throughput tag-sequencing data. Conclusions We found that the expression of many critical genes involved in IAA synthesis and IAA transport was changed after treatment with various concentration of sucrose. Based on the change of these genes expression, IAA and sucrose content, we concluded that sucrose and IAA cooperatively regulated ARs formation. Sucrose affected ARs formation by improving IAA content at induction stage, and increased sucrose content might be also required for ARs development according to the changes tendency after application of exogenous IAA.

The lotus NnWOX1-1、NnWOX4-3 and NnWOX5-1 promoted root formation and enhanced stresses tolerance in transgenic Arabidopsis thaliana

“…Further analysis of sucrose effect on ARs formation shows that it's effect mainly happened at induction period of ARs development [53]. In lotus, sucrose role on ARs formation has been assessed, and sucrose can be considered as IAA to participate in ARs developmental process [22]. In this study, we found that these three genes were all induced by IAA and sucrose, although their expression pro le was different.…”

“…However, whether ethylene signal being involved in drought and salt adaptation is needed further analysis. In previous study, it is founnd that lignin synthesis has a great in uence on ARs development through sucrose pathway [22,23]). In this study, we found that overexpression of NnWOX1-1, NnWOX4-3 and NnWOX5-1 did not NnWOX1-1, NnWOX4-3 and NnWOX5-1 affecting root development of Arabidopsis was not resulted from synthesis of IAA, ABA and lignin.…”

“…Low concentration of IAA promotes the cell differentiation, and high concentration of exogenous IAA results in adverse effect [20]. Light and photosynthetic products (sucrose) is also found to have a great in uence on the formation of ARs [21,22]. It is reported that lignin is involved in lotus ARs formation, which is also regulated by sucrose, suggesting that the development of ARs also has a complex regulatory network in lotus [23].…”

“…Based on previous study, we has discovered that sucrose and IAA affect ARs formation in lotus seedlings [20,22]. Gene expression is also explored, and three members of lotus WOXs family were involved in sucrose and IAA regulation pathway during ARs development.…”

miR160: An Indispensable Regulator in Plant

“…In apple rootstock, over-expressed miR160a reduced ARF16/17 levels and inhibited AR formation, including the number and length ( Meng et al, 2020 ). The miR160- ARF17 module was also an important regulator in the development of AR of poplar and lotus ( Libao et al, 2020 ; Liu et al, 2020 ). It is important to control the auxin/cytokinin balance during nodule development.…”