A sweetpotato (Ipomoea batatas cv. ‘Jinhongmi’) MADS-box protein cDNA (SRD1) has been isolated from an early stage storage root cDNA library. The role of the SRD1 gene in the formation of the storage root in sweetpotato was investigated by an expression pattern analysis and characterization of SRD1-overexpressing (ox) transgenic sweetpotato plants. Transcripts of SRD1 were detected only in root tissues, with the fibrous root having low levels of the transcript and the young storage root showing relatively higher transcript levels. SRD1 mRNA was mainly found in the actively dividing cells, including the vascular and cambium cells of the young storage root. The transcript level of SRD1 in the fibrous roots increased in response to 1000 μM indole-3-acetic acid (IAA) applied exogenously. During the early stage of storage root development, the endogenous IAA content and SRD1 transcript level increased concomitantly, suggesting an involvement of SRD1 during the early stage of the auxin-dependent development of the storage root. SRD1-ox sweetpotato plants cultured in vitro produced thicker and shorter fibrous roots than wild-type plants. The metaxylem and cambium cells of the fibrous roots of SRD1-ox plants showed markedly enhanced proliferation, resulting in the fibrous roots of these plants showing an earlier thickening growth than those of wild-type plants. Taken together, these results demonstrate that SRD1 plays a role in the formation of storage roots by activating the proliferation of cambium and metaxylem cells to induce the initial thickening growth of storage roots in an auxin-dependent manner.

Purpose: This study compared the pain-relieving effects of human milk, sucrose, and distilled water during examinations for retinopathy of prematurity. Methods: Forty-five preterm infants were randomly assigned to receive a pacifier dipped in one of three solutions: human milk (n=14), 24% sucrose (n=15), or distilled water (n=16), 2 minutes before an eye examination. Their pain score, pulse rate, and oxygen saturation were measured at three time points: 5 minutes before the examination, 30 seconds after speculum introduction, and 2 minutes after the examination. Results: The infants' mean gestational age and weight at birth were 33.1±2.1 weeks and 1,842±470 g, respectively. There were no between-group differences in pain relief during the eye examination. The pain score significantly increased both during (p<.001) and after the examinations (p=.003). Oxygen saturation decreased during the examinations (p<.001); however, the infants in the 24% sucrose group showed higher oxygen saturation (p=.047) during the examinations than the infants in the other groups. Conclusion: Sucking on a pacifier dipped in human milk or 24% sucrose did not reduce the pain associated with eye examinations in preterm infants. Pacifiers dipped in sucrose can be used to maintain better oxygen saturation during these examinations.

No abstract