OsNLP3 enhances grain weight and reduces grain chalkiness in rice.

ABSTRACT

Grain weight, a key determinant of yield in rice (Oryza sativa L.), is governed primarily by genetic factors, whereas grain chalkiness, a detriment to grain quality, is intertwined with environmental factors such as mineral nutrients. Nitrogen (N) is recognized for its impact on grain chalkiness, yet the underlying molecular mechanisms remain elusive. This study revealed the pivotal role of rice NODULE INCEPTION-LIKE PROTEIN 3 (OsNLP3) in simultaneously regulating grain weight and grain chalkiness. Our investigation showed that the loss of OsNLP3 leads to a reduction in both grain weight and dimension, in contrast to the enhancement observed with OsNLP3 overexpression. OsNLP3 directly suppresses the expression of OsCEP6.1 and OsNF-YA8, which were identified as negative regulators associated with grain weight. Consequently, two novel regulatory modules, OsNLP3-OsCEP6.1 and OsNLP3-OsNF-YA8, were identified as key players in grain weight regulation. Notably, the OsNLP3-OsNF-YA8 module not only augments grain weight but also mitigates grain chalkiness in response to N. This research clarifies the molecular mechanisms orchestrating grain weight through the OsNLP3-OsCEP6.1 and OsNLP3-OsNF-YA8 modules, underscoring the pivotal role of the OsNLP3-OsNF-YA8 module in alleviating grain chalkiness. These findings offer potential targets for concurrently enhancing rice yield and quality.