**5. Conclusions**

In summary, our results showed that chilling stress induced ROS accumulation, leading to lipid peroxidation and cell death during greening. In particular, our data highlighted the detailed regulation of photosynthetic pigments under chilling stress during greening, suggesting that the inhibition of chlorophyll biosynthesis may be attributable to the blocked synthesis of ALA and the inhibition of conversion from Pchlide into chlorophylls. In this case, we have proposed that application of ALA or overexpression of *HEMA*, *DVR*, and *CHLG* may be good for increasing chlorophyll biosynthesis and improving cold resistance of rice seedlings during greening.

**Supplementary Materials:** Supplementary materials can be found at http://www.mdpi.com/1422-0067/21/4/1390/s1. Figure S1: Relative content of PSI proteins in control and chill-stressed rice seedlings. Figure S2: Relative content of PSI proteins in control and chill-stressed rice seedlings. Table S1: The primers used for quantitative real-time PCR.

**Author Contributions:** M.Y. and S.Y. designed the experiments; Y.Z., Q.H., C.D., Y.H., J.L., and T.C. performed the experiments. S.F., L.Z., Z.Z., and Y.C. analyzed the data and results. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by Sichuan Agricultural University.

**Conflicts of Interest:** The authors declare no conflict of interest.
