Abstract
BackgroundSweet potato (Ipomoea batatas L.) is the sixth most important food crop in the world. The formation and development of storage roots in sweet potato is a highly complicated and genetically programmed process. However, the underlying mechanisms of storage root development have not yet been elucidated.ResultsTo better understand the molecular mechanisms involved in storage root development, a combined analysis of the transcriptome and proteome of sweet potato fibrous roots (F) and storage roots at four different stages (D1, D3, D5 and D10) was performed in the present study. A total of 26,273 differentially expressed genes were identified in a comparison between the fibrous root library and four storage root libraries, while 2558 proteins showed a 1.0-fold or greater expression difference as indicated by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. The combination of the transcriptome and proteome analyses and morphological and physiological data revealed several critical pathways involved in storage root formation and development. First, genes/proteins involved in the development of meristems/cambia and starch biosynthesis were all significantly upregulated in storage roots compared with fibrous roots. Second, multiple phytohormones and the genes related to their biosynthesis showed differential expression between fibrous roots and storage roots. Third, a large number of transcription factors were differentially expressed during storage root initiation and development, which suggests the importance of transcription factor regulation in the development of storage roots. Fourth, inconsistent gene expression was found between the transcriptome and proteome data, which indicated posttranscriptional regulatory activity during the development of storage roots.ConclusionOverall, these results reveal multiple events associated with storage root development and provide new insights into the molecular mechanisms underlying the regulatory networks involved in storage root development.
Highlights
Sweet potato (Ipomoea batatas L.) is the sixth most important food crop in the world
Morphology and anatomy of fibrous roots and storage roots at different stages To elucidate the mechanism of storage root initiation and development, sweet potato roots at five distinct stages of development were collected for measurement of the maximal root diameter (Fig. 1a)
These results indicated that meristem activity is the main driver of storage root formation and development
Summary
Sweet potato (Ipomoea batatas L.) is the sixth most important food crop in the world. Sweet potato (Ipomoea batatas L.) is the sixth most important food crop in the world and is widely grown globally due to its high and stable yield, ease of management, high nutrient content and multiple uses [1, 2]. Wang et al [9] reported that the content of endogenous ABA in the storage roots of Ipomoea batatas is notably higher than that in the non-storage roots of Ipomoea trifida. JA is found at high and low levels in the storage and non-storage roots of Ipomoea trifida, respectively [7], and the exogenous application of JA promotes an increase in storage root diameter by inducing the expansion of cortex cells [13]. The content of GA4 in storage roots is decreased at the early stage, increased at the middle stage, and decreased again at the late stage [9]
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