Growth retardation and differential regulation of expansin genes in chilling-stressed sweetpotato

Plant Biotechnology Reports (Impact Factor: 1.05). 01/2009; 3(1):75-85. DOI: 10.1007/s11816-008-0077-0

ABSTRACT We report here a first evaluation of chilling-responsive gene regulation in the sweetpotato. The growth of sweetpotato plants
was severely retarded at 12°C; the lengths of the leaf, petiole, and root were markedly reduced and microscopic observation
revealed that the elongation growth of the epidermal cells in each of these organs was significantly reduced. We examined
the transcriptional regulation of three sweetpotato expansin genes (IbEXP1, IbEXP2 and IbEXPL1) in response to various chilling temperatures (12, 16, 22, and 28°C). In the leaf and petiole, the highest transcript levels
were those of IbEXP1 at 28°C, whereas IbEXPL1 transcript levels were highest in the root. IbEXP1 mRNA levels in the 12°C-treated petiole showed a fluctuating pattern (transient decrease–recovery–stable decrease) for 48h.
In the leaf and petiole, IbEXP1 and IbEXPL1 exhibited a similar response to chilling in that their mRNA levels decreased at 22°C, increased at 16°C, and decreased dramatically
at 12°C. In contrast, mRNA levels of IbEXP2 in the leaf fell gradually as the temperature fell from 28 to 12°C, while they remained unaltered in the petiole. In the
root, mRNA levels of IbEXPL1 and IbEXP1 reached maximum levels at 16°C, and decreased significantly at 12°C. These data demonstrated that expression of these three
expansin genes was ultimately down-regulated at 12°C; however, transcriptional regulation of each expansin gene exhibited
its own distinctive pattern in response to various chilling temperatures.

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    ABSTRACT: The role of an expansin gene (IbEXP1) in the formation of the storage root (SR) was investigated by expression pattern analysis and characterization of IbEXP1-antisense sweetpotato (Ipomoea batatas cv. Yulmi) plants in an attempt to elucidate the molecular mechanism underlying SR development in sweetpotato. The transcript level of IbEXP1 was high in the fibrous root (FR) and petiole at the FR stage, but decreased significantly at the young storage root (YSR) stage. IbEXP1-antisense plants cultured in vitro produced FRs which were both thicker and shorter than those of wild-type (WT) plants. Elongation growth of the epidermal cells was significantly reduced, and metaxylem and cambium cell proliferation was markedly enhanced in the FRs of IbEXP1-antisense plants, resulting in an earlier thickening growth in these plants relative to WT plants. There was a marked reduction in the lignification of the central stele of the FRs of the IbEXP1-antisense plants, suggesting that the FRs of the mutant plants possessed a higher potential than those of WT plants to develop into SRs. IbEXP1-antisense plants cultured in soil produced a larger number of SRs and, consequently, total SR weight per IbEXP1-antisense plant was greater than that per WT plant. These results demonstrate that SR development was accelerated in IbEXP1-antisense plants and suggest that IbEXP1 plays a negative role in the formation of SR by suppressing the proliferation of metaxylem and cambium cells to inhibit the initial thickening growth of SRs. IbEXP1 is the first sweetpotato gene whose role in SR development has been directly identified in soil-grown transgenic sweetpotato plants.
    Journal of Experimental Botany 09/2012; · 5.24 Impact Factor
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    ABSTRACT: Cell wall modification is an important aspect of plant acclimation to environmental stresses. Structural changes of the existing cell wall mediated by various cell wall modifying proteins help a plant adjust to environmental changes by regulating growth and policing the entry of biotic agents. For example, accelerated shoot growth during submergence and shading allows some plants to escape these unfavorable conditions. This is mediated by the regulation of wall modifying proteins that alter cell wall structure and allow it to yield to turgor, thus fueling cellular expansion. Regulation of cell wall protein activity results in growth modulation during drought, where maintenance of root growth through changes in wall extensibility is an important adaptation to water deficit. Freeze-tolerant plants adjust their cell wall properties to prevent freezing-induced dehydration and also use the cell wall as a barrier against ice crystal propagation. Cell wall architecture is an important determinant of plant resistance to biotic stresses. A rigid cell wall can fend off pathogen attack by forming an impenetrable, physical barrier. When breached, products released during wall modification can trigger plant defense signaling. This review documents and discusses studies demonstrating the importance of timely cell wall modification during plant stress responses by focusing on a well-researched subset of wall modifying proteins.
    Critical Reviews in Plant Sciences 11/2011; 30(6):548-562. · 4.36 Impact Factor


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