The following information accompanied stocks donated to the Bloomington Drosophila Stock Center by S. S. Kim, Jayaraman lab, Janelia Farm Research Campus.
P{20XUAS-Chronos-mVenus} contains the Chronos channelrhodopsin tagged at the C-terminal end with mVenus and expressed under the control of UAS sequences.
P{20XUAS-Chronos-mVenus}attP18 is an insertion into the P{CaryP}attP18 docking site, on the X chromosome.
P{20XUAS-Chronos-mVenus}attP40 is an insertion into the P{CaryP}attP40 docking site, on the 2nd chromosome.
P{20XUAS-Chronos-mVenus}attP2 is an insertion into the P{CaryP}attP2 docking site, on the 3rd chromosome.
P{10XUAS-Chronos-mVenus} contains the Chronos channelrhodopsin tagged at the C-terminal end with mVenus and expressed under the control of UAS sequences.
P{10XUAS-Chronos-mVenus}attP40 is an insertion into the P{CaryP}attP40 docking site, on the 2nd chromosome.
P{10XUAS-Chronos-mVenus}attP2 is an insertion into the P{CaryP}attP2 docking site, on the 3rd chromosome.
P{13XLexAop2-IVS-Chronos-mVenus-p10} contains the Chronos channelrhodopsin tagged at the C-terminal end with mVenus and expressed under the control of lexAop2 sequences.
P{13XLexAop2-IVS-Chronos-mVenus-p10}attP18 is an insertion into the P{CaryP}attP18 docking site, on the X chromosome.
P{13XLexAop2-IVS-Chronos-mVenus-p10}attP40 is an insertion into the P{CaryP}attP40 docking site, on the 2nd chromosome.
P{13XLexAop2-IVS-Chronos-mVenus-p10}attP2 is an insertion into the P{CaryP}attP2 docking site, on the 3rd chromosome.
The channel properties of Chronos were described in 1. The first use of Chronos in flies can be found in section 6.3.3 of 2. What follows is some general information, as well as usage guidelines:
1.    Chronos is the fastest channelrhodopsin available. Compared to CsChrimson or Chrimson, which have slow channel-closing dynamics (time constant: 21.4ms), Chronos's channel-closing time constant is 2.3ms 1. Therefore, Chronos is a preferred choice to generate time-locked spike trains up to 60Hz (up to 10Hz with CsChrimson).
2.    Chronos is slightly green-shifted compared to ChR2 1. Thus, green light (500nm) is the best to activate Chronos and red light (>600nm) cannot activate it. Therefore, experimenters must be careful about visual-system-induced behavioral artifacts if used in behaving flies.
3.    Chronos is not as efficient as CsChrimson, but is at least 20 times more efficient than ChR2 constructs injected in flies. Note that at all light wavelengths (including green), CsChrimson is the most efficient optogenetic reagent available in flies <up>ref 2: Fig. 6.6</up>. The efficiency of Chronos was comparable to ReaChR in behaving flies <up>ref 2: Fig. 6.6</up>.
4.    Overall, if an experiment requires fast and precisely time-locked spike generation at millisecond level temporal resolution and if visually-evoked behavioral artifacts by the use of green light are not major concern, Chronos is the preferred reagent. On the other hand, if visual artifacts are a major concern (e.g., when only weak red light can be used) and spike timing is not important, CsChrimson may be the more useful reagent.
5.    If an experiment is performed in an isolated brain (such as patching a cell in an isolated brain) without optic lobes that respond to light, Chronos may be a very versatile tool. In this case, the only concern would be the efficiency; E.g., if the driver line is not strong enough, then CsChrimson may be the only option.
1 Klapoetke, N.C., Murata, Y., Kim, S.S. et al. (2014) Independent optical excitation of distinct neural populations. Nat Methods  11:338-346 .
2 Kim, S.S., Franconville, R., Turner-Evans, D., Jayaraman, V. (2015) Optogenetics in Drosophila melanogaster. In: New Techniques in Systems Neuroscience (Douglass AD, ed), pp 147-176: Springer International Publishing.