The remarkable features of silk fibroin (SF) from the silkworm (Bombyx mori) have fueled its application as a candidate biomaterial for tissue regeneration and repair. For an ideal scaffold, the rate of degradation should be synchronized to match the rate of new tissue formation, and tuning this rate is essential, as diverse tissues differ in terms of regeneration period. In this Review, we discuss the factors influencing the degradability of SF, which can vary from days to several months, depending on the state of the raw material, the scaffold preparation process, morphological features, and host factors. This knowledge facilitates strategies for tuning the SF degradation rate, including manipulation of molecular weight, crystalline level, and crosslinking degree. Since these strategies have a great influence on the mechanical properties, the superiority of SF has to be sacrificed to satisfy the requirements for degradation rate. We further explore additional strategies, including the incorporation of degradation-promoting supplements such as blending with another polymer (e.g., gelatin) and the incorporation of enzyme-sensitive peptides. The information in this Review will likely aid scientists working with SF materials for the regeneration of diverse tissues.

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Anthocyanins from mulberry fruits are used in medicine. However, little anthocyanin can be detected in other tissues and sometimes also mulberry fruits are colorless. The aim of this study was to investigate which gene or genes have the strongest correlation with the anthocyanin biosynthesis. The expression of several anthocyanin synthesis genes were determined in different tissues of two white and two purple fruit cultivars. Genes encoding dihydroflavonol reductase (MaDFR) and anthocyanidin synthase (MaANS) showed a high expression only in fruit tissue of purple-fruit cultivars. During the development of mulberry fruits, the anthocyanin content was well correlated with the transcripts abundance of MaDFR, MaANS, and MaCHS (encoding chalcone synthase). The skin of female mulberry flowers turns red under irradiance because of up-regulated expressions of MaCHS, MaDFR, and MaANS. These three genes may control the anthocyanin biosynthesis in mulberry and up-regulation of them may greatly increase the anthocyanin content.

Abstract:1-Aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) are encoded by multigene families and are involved in fruit ripening by catalyzing the production of ethylene throughout the development of fruit. However, there are no reports on ACS or ACO genes in mulberry, partly because of the limited molecular research background. In this study, we have obtained five ACS gene sequences and two ACO gene sequences from Morus Genome Database. Sequence alignment and phylogenetic analysis of MaACO1 and MaACO2 showed that their amino acids are conserved compared with ACO proteins from other species. MaACS1 and MaACS2 are type I, MaACS3 and MaACS4 are type II, and MaACS5 is type III, with different C-terminal sequences. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) expression analysis showed that the transcripts of MaACS genes were strongly expressed in fruit, and more weakly in other tissues. The expression of MaACO1 and MaACO2 showed different patterns in various mulberry tissues. MaACS and MaACO genes demonstrated two patterns throughout the development of mulberry fruit, and both of them were strongly up-regulated by abscisic acid (ABA) and ethephon.

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