Proline-rich proteins (PRPs) play several important physiological and
biochemical roles in growth and stress response of plants. A study published
in 3 Biotech reported that the knockout of rice PRP induced cold sensitivity
in rice.

A total of 26 To generation and 16 T1 generation of mutant plants were
generated using CRISPR-Cas9 to explore the role of OsPRP1 in cold stress.
The conserved amino acid sequence was altered and the OsPRP1 expression
level was decreased in mutant plants. The mutant plants exhibited more
sensitivity to cold stress and showed low survival rate with reduced root
biomass than wild-type rice plants. The homozygous mutant line with large
fragment deletion showed higher sensitivity to low temperature. The mutant
lines accumulated less antioxidant enzyme activity and lower levels of
proline, chlorophyll, abscisic acid (ABA), and ascorbic acid (AsA) content
relative to wild-type under low-temperature stress. Furthermore, the
expression of three genes encoding antioxidant enzyme activities was
significantly down-regulated in the mutant lines as compared to wild-type.

The findings suggest that OsPRP1 enhances cold tolerance by modulating
antioxidants and maintaining cross talk through signaling pathways. Thus,
OsPRP1 gene can be used to enhance the cold tolerance trait in rice.

[link.springer.com]