Abstract
Weedy rice is one of the most severe weeds in paddy fields, characterized by its high degree of seed shattering. Abscisic acid (ABA) serves as an abscission-accelerating signal and plays a critical role during abscission. However, mechanisms that link ABA and seed shattering remain elusive. In this study, WR04-6 (shattering) and SN9816 (non-shattering) were used to investigate the expression levels of genes involved in ABA biosynthesis and to determine the levels of ABA in tissues collected from the abscission zone (AZ) and the spikelet. ABA content in WR04-6, particularly in AZ, was significantly higher than in SN9816, significantly increasing prior to abscission. RNA-Sequencing and further expression analyses showed that the expression of OsNCED, the key gene involved in ABA biosynthesis, coincided with the increase of ABA content in the AZ and significantly increased during the seed shattering process. Additionally, the expression analysis of genes related to biosynthesis and metabolism of indole-3-acetic acid, gibberellin acid, and ethylene showed the greatest fold-change. Phytohormone levels associated with ABA co-expression-prediction revealed a potential signal transduction network among plant hormones involved in the regulation of seed abscission. Taken together, data presented in this study suggest that ABA contributes to seed shattering and transiently cooperates with other hormones, triggering a hormone imbalance that leads to the downstream activation of the AZ.
Highlights
Classified as the same species as cultivated rice (Oryza sativa L.) (Cao et al 2006; Reagon et al 2010), weedy rice (Oryza sativa f. spontanea), is one of the most dominant and aggressive weeds found in paddy fields worldwide
A common weedy rice strain WR04-6 (Oryza sativa f. spontanea) and non-seed shattering temperate japonica (Oryza sativa) cultivar SN9816 are significantly different in seed shattering behavior
In WR04-6, a small number of seeds completed the transition from milk to the wax stage, the testa showed a high degree of lignification and the hull color changed from green to dark brown (Fig. 1b)
Summary
Classified as the same species as cultivated rice (Oryza sativa L.) (Cao et al 2006; Reagon et al 2010), weedy rice (Oryza sativa f. spontanea), is one of the most dominant and aggressive weeds found in paddy fields worldwide. Spontanea), is one of the most dominant and aggressive weeds found in paddy fields worldwide It competes with cultivated rice for nutrients, water, sunlight, and other resources affecting crop production (Chauhan and Johnson 2017). In China, weedy rice can reduce rice crop yields by 10–50%, leading to serious economic losses (Zhao et al 2017). It has many morphological and physiological traits related to weediness (black hull, long awn, and red pericarp) and is characterized by its high seed shattering rate (Sun et al 2013, 2019). Studying the mechanism of seed shattering in weedy rice is important for efficient regulation of crop productivity and effective management
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