Identification of HuSWEET Family in Pitaya (Hylocereus undatus) and Key Roles of HuSWEET12a and HuSWEET13d in Sugar Accumulation.

The sugar composition and content of fruit have a significant impact on their flavor and taste. In pitaya, or dragon fruit, sweetness is a crucial determinant of fruit taste and consumer preference. The sugars will eventually be exported transporters (SWEETs), a novel group of sugar transporters that have various physiological functions, including phloem loading, seed filling, nectar secretion, and fruit development. However, the role of SWEETs in sugar accumulation in pitaya fruit is not yet clear. Here, we identified 19 potential members (HuSWEET genes) of the SWEET family in pitaya and analyzed their conserved motifs, physiochemical characteristics, chromosomal distribution, gene structure, and phylogenetic relationship. Seven highly conserved α-helical transmembrane domains (7-TMs) were found, and the HuSWEET proteins can be divided into three clades based on the phylogenetic analysis. Interestingly, we found two HuSWEET genes, HuSWEET12a and HuSWEET13d, that showed strong preferential expressions in fruits and an upward trend during fruit maturation, suggesting they have key roles in sugar accumulation in pitaya. This can be further roughly demonstrated by the fact that transgenic tomato plants overexpressing HuSWEET12a/13d accumulated high levels of sugar in the mature fruit. Together, our result provides new insights into the regulation of sugar accumulation by SWEET family genes in pitaya fruit, which also set a crucial basis for the further functional study of the HuSWEETs.

NT-3 expression in spared DRG and the associated spinal laminae as well as its anterograde transport in sensory neurons following removal of adjacent DRG in cats.

Neurotrophin-3 plays an important role in survival and differentiation of sensory and sympathetic neurons, sprouting of neurites, synaptic reorganization, and axonal growth. The present study evaluated changes in expression of NT-3 in the spinal cord and L6 dorsal root ganglion (DRG), after ganglionectomy of adjacent dorsal roots in cats. NT-3 immunoreactivity increased at 3 days post-operation (dpo), but decreased at 10 dpo in spinal lamina II after ganglionectomy of L1-L5 and L7-S2 (leaving L6 DRG intact). Conversely, NT-3 immunoreactivity decreased on 3 dpo, but increased on 10 dpo in the nucleus dorsalis. Very little NT-3 mRNA signal was detected in the spinal cord, despite the changes in NT-3 expression. The above changes may be related to changes in NT-3 expression in the DRG. Ganglionectomy of L1-L5 and L7-S2 resulted in increase in NT-3 immunoreactivity and mRNA in small and medium-sized neurons, but decreased expression in large neurons of L6 DRG at 3 dpo. It is possible that increased NT-3 in spinal lamina II is derived from anterograde transport from small- and medium-sized neurons of L6 DRG, whereas decreased NT-3 immunoreactivity in the nucleus dorsalis is due to decreased transport of NT-3 from large neurons in the DRG at this time. This notion is supported by observations on NT-3 distribution in the dorsal root of L6 after ligation of the nerve root. The above results indicate that DRG may be a source of neurotrophic factors such as NT-3 to the spinal cord, and may contribute to plasticity in the spinal cord after injury.

Effect of electroacupuncture on neurotrophin expression in cat spinal cord after partial dorsal rhizotomy.

Neuroplasticity of the spinal cord following electroacupuncture (EA) has been demonstrated although little is known about the possible underlying mechanism. This study evaluated the effect of EA on expression of neurotrophins in the lamina II of the spinal cord, in cats subjected to dorsal rhizotomy. Cats received bilateral removal of L1-L5 and L7-S2 dorsal root ganglia (DRG, L6 DRG spared) and unilateral EA. They were sacrificed 7 days after surgery, and the L6 spinal segment removed and processed by immunohistochemistry and in situ hybridization histochemistry, to demonstrate the expression of neurotrophins. Significantly greater numbers of nerve growth factor (NGF) and neurotrophin-3 (NT-3) positive neurons, brain-derived neurotrophic factor (BDNF) immunoreactive varicosities and NT-3 positive neurons and glial cells were observed in lamina II on the acupunctured (left) side, compared to the non-acupunctured, contralateral side. Greater number of neurons expressing NGF mRNA was also observed on the acupunctured side. No signal for mRNA to BDNF and NT-3 was detected. The above findings demonstrate that EA can increase the expression of endogenous NGF at both the mRNA and protein level, and BDNF and NT-3 at the protein level. It is postulated that EA may promote the plasticity of the spinal cord by inducing increased expression of neurotrophins.

[The spatiotemporal change of neurotrophin family and their mRNA expression in spinal cord of cats after partial rhizotomy].

OBJECTIVE: To investigate the spatiotemporal change rule of NGF, BDNF, NT-3 and their mRNA expression in spinal cord of cats after partial dorsal rhizotomy. METHODS: Rhizotomy of unilateral L1-L5, L7-S2 dorsal roots of cats was performed, leaving L6 as a spared dorsal root. By using ABC immunohistochemistry and in situ hybridization techniques, the dynamic changes of the above three factors and their mRNA in spinal lamina II of different segments were analysed. RESULTS: 1. In normal cat, NGF and it's mRNA were detected in part of neurons; BDNF, in nerve fiber terminals, varicosities and neurons; NT-3, in part of neurons, neuroglias and few nerve fiber terminals and varicosities. The mRNAs of the later two were negative. 2. The population of NGF and NGGmRNA positive neurons, NT-3 positive neurons and neuroglias increased significantly 3d-5d after rhizotomy. However, the quantity and density of positive varicosity of BDNF decreased. At 10-11d, the population of NGF and NGF mRNA positive neurons was still on the high level as that at 3-5d, and that of NT-3 began to decrease; the quantity of BDNF recovered to normal except for L, segment, but the density of positive varicosity of BDNF did not yet. The mRNAs of BDNF and NT-3 were still negative. 3. The change of each factor varied with the segments. The highest level time of NGF was earlier in L5, L6 than in L3; the recovery of the quantity of BDNF was the latest in L7; the change of NT-3 positive neuroglia was the same at each segment, but the number of NT-3 positive neuron in L5, L7 returned to normal at 10-11d, and that of L3 did not. CONCLUSION: The three factors all play roles in spinal plasticity after partial rhizotomy, but they function at different time phase and last different time length.

[Effect of acupuncture on the expression of NT3 in the process of spinal plasticity].

OBJECTIVE: To explore the change in the expression of NT3 in the process of promoting the plasticity of spinal cord by acupuncture. METHODS: Five adult cats were subjected to unilateral spared root rhizotomy; their L1-L5, L7-S2 dorsal root ganglia (DRG) were sectioned, but L4 was spared. And two groups of acupoints [Zusani (St.36) and Xuanzhong (G. B.39); Futu (St.32) and Sanyingjiao (Sp.6)] located in hind limb were electro-stimulated for thirty minutes q.d. x 7. At seven days, after acupuncture, the L5 segment of spinal cord and spared dorsal root ganglion (L6) were taken and made into frozen section 20 microns in thickness. Immunohistochemistry (NT3 antibody 1:1500) and in situ hybridization (NT3 cRNA probe 1:100) techniques were used. The numbers of positive neuron for NT3 and it's mRNA in large, medium, small neuron of L6 DRG and the numbers of positive neurons and glia cells for NT3 in lamina II were counted respectively. RESULTS: The numbers of positive large, small neurons for NT3 and its mRNA in DRG and the number of positive neurons and glia cells for NT3 in lamina II on the acupuncture side increased apparently than those on the non-acupuncture side (P < 0.05). However, the positive signal of NT3 mRNA in lamina II was not seen in our study. CONCLUSION: The results indicate that acupuncture promoting the plasticity of spinal cord involves both the increase in expression of NT3 in large and small neurons of spared DRG and the increase in number of NT3 positive neurons and glia cells in spinal lamina II. Moreover, NT3 may play a role in the process of promoting the plasticity of spinal cord by acupuncture.