Inversion induced Manihot esculenta stem tubers express key tuberization genes; Mec1, RZF, SuSy1 and PIN2 (original) (raw)
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Journal of Plant Biochemistry & Physiology, 2013
Cassava (Manihot esculenta) is normally propagated by stem cuttings planted in a slanted, vertical or horizontal orientation. Axillary buds produce aerial shoot and adventitious roots are produced at the base (proximal end) of the cutting, some of which develop into tuberous roots. However, when cuttings are planted in an inverse, slanted or inverse straight orientation, the buried bases of the shoots which arise from underground buds swell. In this study, we determined that the stem swelling accumulates and store starch as do the tuberous root tubers. This phenomenon designated as inversion-induced stem tuberization, first detailed here, provides a system which could be used to study the roles of phytohormones and light.
Auxin signaling and vascular cambium formation enables storage metabolism in cassava tuberous roots
Journal of Experimental Botany
Cassava storage roots are among the most important root crops worldwide and represent one of the most consumed staple foods in Sub-Saharan Africa. The vegetatively propagated tropical shrub can form many starchy tuberous roots from its stem. These storage roots are formed through the activation of secondary root growth processes. However, the underlying genetic regulation of storage root development is largely unknown. Here we report on distinct structural and transcriptional changes occurring during the early phases of storage root development. A pronounced increase in auxin-related transcripts and the transcriptional activation of secondary growth factors, as well as a decrease in gibberellin-related transcripts was observed during the early stages of secondary root growth. This was accompanied by increased cell wall biosynthesis, increased most notably during the initial xylem expansion within the root vasculature. Starch storage metabolism was activated only after the formation ...
Aims Cassava (Manihot esculenta) has three adventitious root types: primary and secondary fibrous roots, and storage roots. Different adventitious root types can also regenerate from in vitro cultured segments. The aim of this study was to investigate aspects of in vitro production of storage roots. † Methods Morphological and anatomical analyses were performed to identify and differentiate each root type. Twenty-nine clones were assayed to determine the effect of genotype on the capacity to form storage roots in vitro. The effects of cytokinins and auxins on the formation of storage roots in vitro were also examined. † Key Results Primary roots formed in vitro and in vivo had similar tissue kinds; however, storage roots formed in vitro exhibited physiological specialization for storing starch. The only consistent diagnostic feature between secondary fibrous and storage roots was their functional differentiation. Anatomical analysis of the storage roots formed in vitro showed that radial expansion as a consequence of massive proliferation and enlargement of parenchymatous cells occurred in the middle cortex, but not from cambial activity as in roots formed in vivo. Cortical expansion could be related to dilatation growth favoured by hormone treatments. Starch deposition of storage roots formed in vitro was confined to cortical tissue and occurred earlier than in storage roots formed in vivo. Auxin and cytokinin supplementation were absolutely required for in vitro storage root regeneration; these roots were not able to develop secondary growth, but formed a tissue competent for starch storing. MS medium with 5 % sucrose plus 0 . 54 mM 1-naphthaleneacetic acid and 0 . 44 mM 6-benzylaminopurine was one of the most effective in stimulating the storage root formation. Genotypes differed significantly in their capacity to produce storage roots in vitro. Storage root formation was considerably affected by the segment's primary position and strongly influenced by hormone treatments. † Conclusions The storage root formation system reported here is a first approach to develop a tuberization model, and additional efforts are required to improve it. Although it was not possible to achieve root secondary growth, after this work it will be feasible to advance in some aspects of in vitro cassava tuberization.
Protein & Peptide Letters, 2004
Cassava storage roots result from swelling of adventitious roots by secondary growth. In the present study we aimed to gain insight into the molecular processes occurring during cassava storage root formation. We report a comparative gene expression study in adventitious and storage roots in order to identify genes possibly related to storage organ formation. Our results revealed five genes with higher expression levels in secondary xylem of storage roots than adventitious roots. Among them, the Mec1 gene coding for Pt2L4 glutamic acid-rich protein and a putative RING Zinc Finger and LEA protein genes were strongly induced in secondary xylem tissue.
Development of Tuberous Cassava Roots under Different Tillage Systems: Descriptive Anatomy
Plant Production Science, 2015
The interaction between the roots of cassava (Manihot esculenta Crantz) and soil physical properties has previously been analyzed. This interaction results in differences in production of plant material and in the physicochemical features of the roots, suggesting that changes in soil physical conditions may be related to changes in root anatomy. This work described the anatomical development of the tuberous cassava roots (cv. IAC 576-70) under different tillage systems. Roots grown under three different tillage systems (minimum, conventional and no tillage) were examined at 15, 30, 60, 90, 120, 150 and 180 days after planting (DAP). The tillage systems did not appear to influence root anatomy during root development; at 15 and 30 DAP roots had early secondary growth; at 60 DAP the process of tuber formation had started; at 90 DAP the secondary xylem had completely differentiated to allow storage of starch; at 120, 150 and 180 DAP roots exhibited a similar anatomical structure to that observed at 90 DAP. From these results we conclude that the anatomical structure of cassava tuberous roots is established by 90 DAP and the sequence of establishment and development of tissues that make up the tuberous roots is not influenced by tillage systems during the first 180 DAP.
Set up from the beginning:The origin and early development of cassava storage roots
Despite the importance of storage root (SR) organs for cassava and the other root crops yield, their developmental origin is poorly understood. Here we use multiple approaches to shed light on the initial stages of root development demonstrating that SR and fibrous roots (FR) follow different rhizogenic processes. Transcriptome analysis carried out on roots collected before, during and after root bulking highlighted early and specific activation of a number of functions essential for root swelling and identified root-specific genes able to effectively discriminate emerging FR and SR. Starch and sugars start to accumulate at a higher rate in SR before they
Journal of Plant Growth Regulation, 2011
A faster system to get tuberous roots from in vitro cultured cassava plants may enhance the process of exploring the function and practical application of some root-specific expressed genes. The effects of cytokinin, auxin, sucrose, maltose, and glucose on development of shoots and tuberous roots and plantlet regeneration of in vitro cultured cassava were investigated in this study. The cytokinin N-benzyladenine (BA) (0–2.0 mg l−1) was effective on shoot regeneration. The auxin α-naphthalene acetic acid (NAA) (0–2.0 mg l−1) proved to be effective on root development. Plantlets with fibrous roots easily generated tuberous roots in vitro. The tuberous roots were induced only when both BA and NAA were used in combination. MS medium supplemented with sucrose at 175 mM (or 6% w/v) resulted in the highest frequencies of shoot induction (71.43%) and average fresh weight (0.61 g) of tuberous roots when BA (0.5 mg l−1) and NAA (0.5 mg l−1) were also added to the MS medium.