The lipid transfer protein OsLTPL159 is involved in cold tolerance at the early seedling stage in rice

Nonspecific lipid transfer proteins (nsLTPs) play critical roles in plant development and response to abiotic stresses. Here, we found that a rice lipid transfer protein, OsLTPL159, was associated with cold tolerance at the early seedling stage. Overexpression of an OsLTPL159(IL)(112) allele from the cold-tolerant introgression line IL112 in either the japonica variety Zhonghua17 (ZH17) or the indica variety Teqing background dramatically enhanced cold tolerance. In addition, down-regulation of the expression of OsLTPL159 in the japonica variety ZH17 by RNA interference (RNAi) significantly decreased cold tolerance. Further transcriptomic, physiological and histological analysis showed that the OsLTPL159(IL)(112) allele likely enhanced the cold tolerance of rice at the early seedling stage by decreasing the toxic effect of reactive oxygen species, enhancing cellulose deposition in the cell wall and promoting osmolyte accumulation, thereby maintaining the integrity of the chloroplasts. Notably, overexpression of another allele, OsLTPL159(GC)(2), from the recipient parent Guichao 2 (GC2), an indica variety, did not improve cold tolerance, indicating that the variations in the OsLTPL159 coding region of GC2 might disrupt its function for cold tolerance. Further sequence comparison found that all 22 japonica varieties surveyed had an OsLTPL159 haplotype identical to IL112 and were more cold-tolerant than the surveyed indica varieties, implying that the variations in OsLTPL159 might be associated with differential cold tolerance of japonica and indica rice. Therefore, our findings suggest that the OsLTPL159 allele of japonica rice could be used to improve cold tolerance of indica rice through a molecular breeding strategy.