FLOURY SHRUNKEN ENDOSPERM1 Connects Phospholipid Metabolism and Amyloplast Development in Rice

Abstract

Starch synthesized and stored in amyloplasts serves as the major energy storage molecule in cereal endosperm. To elucidate the molecular mechanisms underlying amyloplast development and starch synthesis, we isolated a series of floury endosperm mutants in rice (). We identified the rice mutant (), which exhibited obvious defects in the development of compound starch grains, decreased starch content, and altered starch physicochemical features. Map-based cloning showed that encodes a phospholipase-like protein homologous to phosphatidic acid-preferring phospholipase A was expressed ubiquitously with abundant levels observed in developing seeds and roots. FSE1 was localized to both the cytosol and intracellular membranes. Lipid profiling indicated that total extra-plastidic lipids and phosphatidic acid were increased in plants, suggesting that FSE1 may exhibit in vivo phospholipase A activity on phosphatidylcholine, phosphatidylinositol, phosphatidyl-Ser, phosphatidylethanolamine, and, in particular, phosphatidic acid. Additionally, the total galactolipid content in developing endosperm was significantly reduced, which may cause abnormal amyloplast development. Our results identify FSE1 as a phospholipase-like protein that controls the synthesis of galactolipids in rice endosperm and provide a novel connection between lipid metabolism and starch synthesis in rice grains during endosperm development.

Inactivation of rice starch branching enzyme IIb triggers broad and unexpected changes in metabolism by transcriptional reprogramming

“…The down-regulation of AGPase also increased fatty acid accumulation in sugarcane and potato (63,64). In the rice floury shrunken endosperm 1 (fse1) mutant, the reduction in total starch and amylose levels was complemented by a ∼48% increase in total lipids (65). The ∼26% loss of total starch in line E15 is therefore consistent with the increase in fatty acid levels, although the levels of lauric acid (C12:0) remained stable, perhaps because amylose can form complexes with longer-chain fatty acids (66).…”

Comprehensive comparison and applications of different sections in investigating the microstructure and histochemistry of cereal kernels

“…S2A-C). For starch observation, the iodine solution is the best choice [20,[52][53][54] (Additional file 1: Fig. S3).…”

Recent Advances in the Cellular and Developmental Biology of Phospholipases in Plants

“…The gene FSE1 encodes a PL-like protein that is homologous to the PA-preferring PLA 1 s and controls the synthesis of galactolipids in the rice endosperm. It is important for seed and endosperm development (Long et al., 2018). Furthermore, PLA 1 s may also have root-specific functions.…”