No abstract

No abstract

Lychee is an exotic tropical fruit with a distinct flavor. The genome of cultivar ‘Feizixiao’ was assembled into 15 pseudochromosomes, totaling ~470 Mb. High heterozygosity (2.27%) resulted in two complete haplotypic assemblies. A total of 13,517 allelic genes (42.4%) were differentially expressed in diverse tissues. Analyses of 72 resequenced lychee accessions revealed two independent domestication events. The extremely early maturing cultivars preferentially aligned to one haplotype were domesticated from a wild population in Yunnan, whereas the late-maturing cultivars that mapped mostly to the second haplotype were domesticated independently from a wild population in Hainan. Early maturing cultivars were probably developed in Guangdong via hybridization between extremely early maturing cultivar and late-maturing cultivar individuals. Variable deletions of a 3.7 kb region encompassed by a pair of CONSTANS-like genes probably regulate fruit maturation differences among lychee cultivars. These genomic resources provide insights into the natural history of lychee domestication and will accelerate the improvement of lychee and related crops.

1 The aim of this study was to identify the presence of matrix metalloproteinase-9 (MMP-9) in human platelets and systematically examine its inhibitory mechanisms of platelet activation. 2 In this study, we report on an efficient method for the quantitative analysis of pro-MMP-9 in human platelets using capillary zone electrophoresis (CZE). To elucidate subcellular localization of MMP-9 in human platelets, we investigated intraplatelet MMP-9 by immunogold labeling and visualized it using electron microscopy. In an in vivo thrombotic study, platelet thrombus formation was induced by irradiation of mesenteric venules with filtered light in mice pretreated with fluorescein sodium. 3 MMP-9-gold labeling was observed on the plasma membrane, a-granules, open canalicular system, and within the cytoplasma both in resting and activated platelets. Furthermore, activated MMP-9 concentration-dependently (15-90 ng ml À1 ) inhibited platelet aggregation stimulated by agonists. Activated MMP-9 (21 and 90 ng ml À1) inhibited phosphoinositide breakdown, intracellular Ca 2 þ mobilization, and thromboxane A 2 formation in human platelets stimulated by collagen (1 mg ml À1). In addition, activated MMP-9 (21 and 90 ng ml À1 ) significantly increased the formation of nitric oxide/cyclic GMP. 4 Rapid phosphorylation of a platelet protein of Mr 47,000 (P47), a marker of protein kinase C activation, was triggered by phorbol-12, 13-dibutyrate (PDBu) (60 nM). This phosphorylation was markedly inhibited by activated MMP-9 (21 and 90 ng ml À1). Activated MMP-9 (1 mg g À1 ) significantly prolonged the latency period of inducing platelet plug formation in mesenteric venules. 5 These results indicate that the antiplatelet activity of activated MMP-9 may be involved in the following pathways. (1) Activated MMP-9 may inhibit the activation of phospholipase C, followed by inhibition of phosphoinositide breakdown, protein kinase C activation, and thromboxane A 2 formation, thereby leading to inhibition of intracellular Ca 2 þ mobilization. (2) Activated MMP-9 also activated the formation of nitric oxide/cyclic GMP, resulting in inhibition of platelet aggregation. These results strongly indicate that MMP-9 is a potent inhibitor of aggregation. It may play an important role as a negative feedback regulator during platelet activation.