Table 2 Strains and plasmids used in this study

Strains

 E. coli

  DH5α

Host strain for cloning

Invitrogen

  ET12567/pUZ8002

Donor strain for conjugation

Kieser et al. [37]

 S. bingchenggensis

The milbemycin-producing strain

Wang et al. [14]

 S. avermitilis

  NA-108

Mutant strain of S. avermitilis NEAU1069 producing “B” components of avermectins as main secondary metabolites

This study

  AVE-T27

Mutant strain of NA-108 with the replacement of aveDH2-KR2 by milDH2-ER2-KR2

This study

  AVE-H39

Mutant strain of AVE-T27 with the replacement of aveLAT-ACP by milLAT-ACP

This study

Plasmids

  pUC19

Cloning vector for E. coli, Amp ^R

TaKaRa

  pKC1139

E. coli-Streptomyces shuttle vector, Am ^R

Kieser et al. [37]

  pER-1

pUC19 derivative containing aveDH2-KR2 upstream fragment, Amp ^R

This study

  pER-2

pUC19 derivative containing aveDH2-KR2 upstream and downstream fragments, Amp ^R

This study

  pER-3

pUC19 derivative containing milDH2-ER2-KR2 together with aveDH2-KR2 upstream and downstream fragments, Amp ^R

This study

  pER-4

pKC1139 derivative containing milDH2-ER2-KR2 together with aveDH2-KR2 upstream and downstream fragments, Am ^R

This study

  pLM-1

pMD19-T derivative containing milLAT-ACP together with aveLAT-ACP upstream and downstream fragments, Amp ^R

This study

  pLM-2

pKC1139 derivative containing milLAT-ACP together with aveLAT-ACP upstream and downstream fragments, Amp ^R

This study