Nitrate transporters are primarily responsible for absorption of nitrate from soil and nitrate translocation among different parts of plants. They deliver nitrate to where it is needed. However, recent studies have revealed that nitrate transporters are extensively involved in coping with adverse environmental conditions besides limited nitrate/nitrogen availability. In this review, we describe the functions of the nitrate transporters related to abiotic stresses and their regulation. The expected and unexpected roles of nitrate transporters in plant abiotic stress resistance will also be discussed.

Moderate soil drying imposed at the post-anthesis stage significantly increases starch accumulation in inferior grains of rice, but how this process is regulated at the level of gene expression remains unclear. In this study, we applied moderate drying (MD) treatments to the soil at the post-anthesis stage and followed the dynamics of the conversion process of soluble sugars to starch in inferior grains using RNA-seq analysis. An elevated level of ABA induced by MD was consistently associated with down-regulation of ABA8ox2, suggesting that lower expression of this gene may be responsible for the higher ABA content, potentially resulting in better filling in inferior grains. In addition, MD treatments up-regulated genes encoding five key enzymes involved sucrose-to-starch conversion and increased the activities of enzymes responsible for soluble-sugar reduction and starch accumulation in inferior grains. Differentially expressed transcription factors, including NAC, GATA, WRKY, and M-type MADS, were predicted to interact with other proteins in mediating filling of inferior grains as a response to MD. Transient expression analysis showed that NAC activated WAXY expression by binding to its promoter, indicating that NAC played a key role in starch synthesis of inferior grains under MD treatment. Our results provide new insights into the molecular mechanisms that regulate grain filling in inferior grains of rice under moderate soil drying.

Both the filling and development of grain are key processes determining agriculture production and reproductive growth in rice. The processes of grain filling and endosperm development are crucial for the accumulation of major storage compounds in rice grains. This requires extensive remobilization of carbon reserves from source to sink and the precise regulation of sucrose‐to‐starch conversion. Both the developmental sequence of the panicle and environmental signals influence the carbon flow between the leaves, leaf sheath, stem, and spikelets during grain filling. This, in turn, affects endosperm development and the production of storage compounds. In this review, we synthesize recent insight into grain development in rice, focusing on the dynamic changes in phytohormones and how their homeostasis integrates developmental and environmental cues to control grain filling in the developing panicle. We also highlight recent advances in the genetic control of carbohydrate remobilization and the transcriptional regulatory networks governing carbohydrate metabolism and grain development in rice. The asynchronous initiation and imbalance in grain filling limit the full yield potential of cereal crops. The “superior/inferior spikelets” serve as a model system for understanding the regulatory mechanisms underlying grain filling and development. Systematic research on carbohydrate flow and phytohormone crosstalk could enhance our understanding of optimizing yield production in cereal crops. Additionally, a thorough analysis of key genetic regulatory mechanisms can offer a genetic foundation and targets for precisely adjusting grain filling traits, ultimately aiding in the development of high‐yield crop varieties.