Gene Regulatory Network Guided Investigations and Engineering of Storage Root Development in Root Crops

Abstract

The plasticity of plant development relies on its ability to balance growth and stress resistance. To do this, plants have established highly coordinated gene regulatory networks (GRNs) of the transcription factors and signaling components involved in developmental processes and stress responses. In root crops, yields of storage roots are mainly determined by secondary growth driven by the vascular cambium. In relation to this, a dynamic yet intricate GRN should operate in the vascular cambium, in coordination with environmental changes. Despite the significance of root crops as food sources, GRNs wired to mediate secondary growth in the storage root have just begun to emerge, specifically with the study of the radish. Gene expression data available with regard to other important root crops are not detailed enough for us directly to infer underlying molecular mechanisms. Thus, in this review, we provide a general overview of the regulatory programs governing the development and functions of the vascular cambium in model systems, and the role of the vascular cambium on the growth and yield potential of the storage roots in root crops. We then undertake a reanalysis of recent gene expression data generated for major root crops and discuss common GRNs involved in the vascular cambium-driven secondary growth in storage roots using the wealth of information available in Arabidopsis. Finally, we propose future engineering schemes for improving root crop yields by modifying potential key nodes in GRNs.

Comparative Transcriptome Profiling Reveals the Genes Involved in Storage Root Expansion in Sweetpotato (Ipomoea batatas (L.) Lam.)

“…Transcription factors can specifically bind to cis-acting elements in the promoter region of eukaryotic genes to induce or inhibit the transcription of the downstream targets [ 35 ]. The development of SR or tuber in tuber crops mostly relies on transcription factor regulation, including starch metabolism and hormone biosynthesis and transport [ 17 ].…”

Genome-wide identification and characterization of the sweet potato (Ipomoea batatas (L.) Lam.) ARF, Aux/IAA, GH3 and SAUR gene families reveal their putative role in tuberization

“…The expression analysis supported the reports that ARFs participate in tuberization. The S. tuberosum homolog of IbARF8, i.e., StARF8, is a potato tuberization marker that is regulated by StBEL5-POTH1 (BEL5-LIKE HOMEODOMAIN -POTATO HOMEOBOX 1) [41]. Pratt and Zhang [19] found that ItfARF8 was expressed highly in root tissue and is likely to have important roles during tuberization.…”

Seasonal Variation in Transcriptomic Profiling of Tetrastigma hemsleyanum Fully Developed Tuberous Roots Enriches Candidate Genes in Essential Metabolic Pathways and Phytohormone Signaling

“…The development of TRs and tubers is a complex process, which depends on the balances between endogenous factors, such as phytohormones, sucrose, and starch, and exogenous environmental factors, including temperature, drought, photoperiod, and nutrient status (Khan et al, 2016;Utsumi et al, 2020). The mechanism of tuberous organ formation has been widely studied in root crops such as sweetpotato (Ipomoea batatas), potato (Solanum tuberosum), and cassava (Manihot esculenta) (Tanaka, 2016;Hoang et al, 2020), indicating the role of endogenous phytohormones, sucrose, and starch in the development of TR. Cytokinins (CTKs) (Tanaka et al, 2008;Sojikul et al, 2015), auxins (Faivre-Rampant et al, 2004;Noh et al, 2010;Roumeliotis et al, 2012;Sojikul et al, 2015), jasmonic acid (JA) (Koda et al, 2001;Cenzana et al, 2003), and brassinosteroids (BRs) (Wei and Li, 2016;Que et al, 2018;Hoang et al, 2020) improve the initiation of TR.…”

“…The mechanism of tuberous organ formation has been widely studied in root crops such as sweetpotato (Ipomoea batatas), potato (Solanum tuberosum), and cassava (Manihot esculenta) (Tanaka, 2016;Hoang et al, 2020), indicating the role of endogenous phytohormones, sucrose, and starch in the development of TR. Cytokinins (CTKs) (Tanaka et al, 2008;Sojikul et al, 2015), auxins (Faivre-Rampant et al, 2004;Noh et al, 2010;Roumeliotis et al, 2012;Sojikul et al, 2015), jasmonic acid (JA) (Koda et al, 2001;Cenzana et al, 2003), and brassinosteroids (BRs) (Wei and Li, 2016;Que et al, 2018;Hoang et al, 2020) improve the initiation of TR. However, the level of auxin has been shown to decrease gradually during the secondary thickening growth of the TR (Tanaka et al, 2008;Noh et al, 2010;Dong et al, 2019;.…”

“…The accumulation and metabolism of starch and sucrose form the basis of plant growth and development and play an important role in the development of TRs (Wang S. et al, 2006;Villordon et al, 2014;Hoang et al, 2020). Starch is one of the main storage compounds in TR, and some genes in starch metabolism, including those encoding β-amylase, ADP-glucose pyrophosphorylase (AGPase), α-1-4 glucan phosphorylase, and starch synthase (SS) (Wang S. et al, 2006;Firon et al, 2013;Ponniah et al, 2017), have been shown to be upregulated during the initiation and growth of TR (Firon et al, 2013;Villordon et al, 2014).…”