Although Asian type HLB is regarded as heat-tolerant, our literature review and analysis of climate data suggest that high summer temperature appears to restrict HLB distribution and occurrence. HLB worldwide distribution and severity appear to be impacted by high summer temperature - HLB is the most severe in the subtropical and tropical regions with moderate summer temperature maxima. Florida in the US, São Paulo in Brazil, Guangdong in China, and severe HLB occurrence regions share this climate characteristic.

Aging is associated with increased incidence of myocardial infarctions and impaired angiogenesis - new capillary blood vessel formation from preexisting vessels. The molecular mechanism(s) of aging-related impairment of angiogenesis are unknown. In the present study we focused on the mechanism of activation of the gene for vascular endothelial growth factor (VEGF - the most potent stimulator of angiogenesis) in young and aging myocardial microvascular endothelial cells (MMEC). Activation of VEGF gene in the cell nucleus is mediated in part by the transcription factor hypoxia-inducible factor 1 alpha (HIF1 alpha). In order to activate VEGF gene, HIF1 alpha must first be transported to the nucleus, but the mechanisms of this transport are unknown. We hypothesized that reduced VEGF gene activation and impaired angiogenesis in myocardium during aging can result from downregulation of the nuclear transport receptor - importin alpha that leads to decreased transport of HIF1 alpha to the nucleus. We examined in MMEC isolated from young (3 months of age) and aging (24 months old) Fisher F-344 rats: 1) in vitro angiogenesis; and 2) the expression of VEGF, importin alpha and HIF1 alpha. Aging MMEC exhibited a 3.7-fold reduction in angiogenesis and a corresponding reduction in VEGF (by 3-fold) and importin alpha (by 1.9-fold) levels compared to young MMEC. Aging MMEC also exhibited cytoplasmic accumulation (by 1.8-fold) of HIF1 alpha protein, reduced HIF1 alpha transport to the nucleus and decreased binding of HIF1 alpha protein to the VEGF gene promoter. This study is the first demonstration of the downregulation of importin alpha in aging MMEC and reduced nuclear transport of HIF1 alpha, which likely lead to decreased VEGF gene activation and impaired angiogenesis.

“Candidatus Liberibacter asiaticus” is associated with citrus Huanglongbing (HLB, yellow shoot disease), a highly destructive disease currently threatening world citrus production. HLB has a long history in China and was found in Brazil in 2004 and U.S.A. in 2005.  There is an urgent need to differentiate isolates of “Ca. L. asiaticus” from different geographical regions for effective control of HLB.  In this study, isolates of “Ca. L. asiaticus” collected from Brazil, China and the United States were evaluated based on two previously characterized genomic loci, one locus (trn1) with variable tandem repeat numbers (TRNs), and the other locus (snp1) is characteristic in single nucleotide polymorphisms (SNPs).  A total of 299 strains (84 Brazil, 132 China and 83 U.S.) were analyzed.  At the trn1 locus, “Ca. L. asiaticus” strains were divided into TRN-A and TRN-B groups.  TRN-A isolates dominated the China and U.S. populations but were not detected in the Brazil isolates.  In contrast, TRN-B dominated the Brazil isolates but occurred at low frequencies in China (3%) and U.S. (6%).  SNP Analyses at the snp1 locus established Term-A and Term-G groups.  Term-A group included all Brazil and China isolates, along with 6% U. S. isolates which were also TRN-B isolates.  The remaining (94%) U. S. isolates were in Term-G group.  By combining data from the analyses of the two genomic loci, it is shown that the TRN-A:Term A genotype was unique to China, TRN-A:Term-G genotype was unique to U.S., and the TRN-B:Term-A genotype dominated the Brazil isolates.  No TRN-B:Term-B isolates were found.

Ghrelin, a hormone produced mainly by gastric mucosal cells stimulates growth hormone (GH) release. Ghrelin is also expressed in the endothelial cells of blood vessels suggesting its physiological role and a function in these cells. We recently demonstrated that ghrelin induces angiogenesis--new capillary blood vessel formation- in neonatal human microvascular endothelial cells (HMVECs). Angiogenesis is impaired in aging individuals both in vitro and in vivo, but the precise mechanism(s) of this phenomenon is unknown. We examined whether HMVECs derived from aging individuals (66 years and 90 years old), 66-HMVECs and 90-HMVECs have reduced ghrelin levels vs. neonatal (Neo) HMVECs and whether treatment with exogenous ghrelin can restore impaired in vitro angiogenesis on matrigel in aged HMVECs. Ghrelin levels were reduced in the aged HMVECs by 3.2-fold (p<0.05) compared to Neo-HMVECs. Angiogenesis was significantly decreased in the aged 66- and 90-HMVECs by 39.7% (p = 0.003) and 62.4% (p = 0.003), respectively compared to Neo-HMVECs. Treatment with exogenous ghrelin significantly reversed impaired angiogenesis in aged HMVECs with the EC(50) 0.05 nM. Ghrelin induced angiogenesis in Neo-HMVECs mainly through ERK2 activation. This study is the first demonstration that reduced ghrelin is one of the factors responsible for aging-related impairment of angiogenesis.

Huanglongbing (HLB, yellow shoot disease) is devastating citrus production worldwide. No effective control measure is currently available. In China, management of HLB through nutrient applications was raised in the past and the interest is renewed recently. In this study, the efficacy of a soil conditioner on different ages of huanglongbing (HLB)-affected citrus trees was evaluated at 3 orchards in Sihui and at different months post treatment in Longmen, Guangdong province. Two species, Shatangju (Citrus. reticulate Blanco cv. Shatang ju) and Chuntianju (C. reticulate cv. Chuntian Ju) were evaluated in a completely random design. Symptomatical observation indicated that the treated plants, especially young tree, had more new shoots and young leaves than the untreated plants. In addition, the young leaves on treated plants looked healthy, with few HLB symptoms, compared to the untreated plants. Real-time PCR results indicated a significant “Candidatus Liberibacter asiaticus” (“Las”) reduction in the treated 2-year old citrus plants (p=0.005). “Las” titers were reduced by 2.19 and 2.45 times in the leaves of treated plants, compared to those of untreated 3 and 8-year-old affected Shatangju trees. Statistical data from different aged Shatangju trees showed “Las” titers were significantly positively related with treatment (P=0.004) and age of trees (P=0.022), but not with old and young leaves (P>0.05). Comparative analysis of the efficacy of soil conditioner treatment in 4-year-old Chuntianju at 2, 4, and 7 month-post treatment (mpt) showed that the quantities of “Llas” were significantly lower in newly growing leaves at 7 mpt (94.51% decrease or 2.59 times lower than those at 4 or 2 mpt, p=0.002). Bacterial titers in treated plants were significantly lower (34.12% decrease) than control plants, and 82.72% lower in young leaves than in mature leaves. The P values of treatment (treated and untreated), leaf part (old leaf and new leaf), and sampling time (at different months after treatment) were P=0.014, P<0.001, and P<0.001, respectively. The Soil conditioner test revealed that the P, N, K, organic matter, and Mn contents in the soil conditioner-treated orchard soil were all significantly higher than in the non-treated soil at 2 mpt (p<0.05). Unexpectedly, microflora at the treated and nontreated sites in the orchards seemed to have no apparent difference in total viable colony numbers and microorganism types. Semi-quantitative RT-PCR found most defense response genes increased in the treated plants. On the other hand, most starch synthesis related genes, including genes coding for a phloem-specific lectin PP2-like protein, were more stongly expressed in the untreated plants. This study suggests that the soil conditioner not only works as a fertilizer, but also can play a role in ”Las” titer management.