Anther dehiscence controls optimal interaction between pollen and stigma, thereby determining the successful sexual reproduction. The regulators or mechanisms of this process remain elusive. Here, two CRISPR/Cas9 mutants of a rice exocyst subunit gene SEC3A, sec3a-1 and sec3a-2, showed anther indehiscence at anthesis and male sterility at maturity. Pollen viability and germination in the mutants were partly defective, whereas their female gametes undergone a normal development. Hybrid or self-pollinated seeds could be produced by artificial pollination, suggesting potential use of a weak sec3a mutant as a female line during hybrid breeding. SEC3A is widely expressed in various tissues, including anther walls. Further results showed an excessive IAA accumulation and no endothecium lignification in sec3a-1/2 anthers. Our findings suggest that SEC3A appears to regulate anther dehiscence by modulating auxin signaling, providing insights into regulation of anther dehiscence and function of exocyst in plants.

As a major subunit of the exocyst complex, members of the EXO70 family have mainly been shown to play roles in cell polarity and morphogenesis in Arabidopsis, but their roles in plant endosymbiosis, such as with arbuscular mycorrhizal fungi (AMF), have rarely been reported. Here, using knockout and overexpression lines, we show that OsEXO70L2, which encodes a divergent EXO70 protein in rice, controls the number of primary roots and is essential for large lateral root formation. Furthermore, the OsEXO70L2 mutant sr1 displayed rare internal AMF hyphae and no arbuscules. We also found that AMF sporulation can occur in roots despite low colonization and that AMF colonization and sporulation are modulated by photoperiod and co-culture with clover. Finally, genes related to auxin homeostasis were found to be affected in the OsEXO70L2 knockout or overexpression lines, suggesting that auxin is at least partly responsible for the phenotypes. This study provides new perspectives on the role of the exocyst complex during root development and AM in rice.

A dynamic plant architecture is the basis of plant adaptation to changing environments. Although many genes regulating leaf rolling have been identified, genes directly associated with water homeostasis are largely unknown. Here, we isolated a rice mutant, dynamic leaf rolling 1 (dlr1), characterized by ‘leaf unfolding in the morning-leaf rolling at noon-leaf unfolding in the evening’ during a sunny day. Water content was decreased in rolled leaves and water sprayed on leaves caused reopening, indicating that in vivo water deficiency induced the leaf rolling. Map-based cloning and expression tests demonstrated that an A1400G single base mutation in Oryza sativa Polygalacturonase 1 (OsPG1)/PHOTO-SENSITIVE LEAF ROLLING 1 (PSL1) was responsible for the dynamic leaf rolling phenotype in the dlr1 mutant. OsPG1 encodes a polygalacturonase, one of the main enzymes that degrade demethylesterified homogalacturonans in plant cell walls. OsPG1 was constitutively expressed in various tissues and was enriched in stomata. Mutants of the OsPG1 gene exhibited defects in stomatal closure and decreased stomatal density, leading to reduced transpiration and excessive water loss under specific conditions, but had normal root development. Further analysis revealed that mutation of OsPG1 led to reduced pectinase activity in the leaves and increased demethylesterified homogalacturonans in guard cells. Our findings reveal a mechanism by which OsPG1 modulates water homeostasis to control dynamic leaf rolling, providing insights for plants to adapt to environmental variation.

Grain filling influences grain size and quality in cereal crops. The molecular mechanisms that regulate grain endosperm development remain elusive. In this study, we characterized a filling-defective and grain width mutant, fgw1, whose mutation increased rice seed width mainly via cell division and expansion in grains. Sucrose contents were higher but starch contents lower in the fgw1 mutant during the grain-filling stage, resulting in inferior endosperm of opaque, white appearance with loosely packed starch granules. Map-based cloning revealed that FGW1 encoded a protein containing DUF630/DUF632 domains, localized in the plasma membrane with preferential expression in the panicle. RNA interference in FGW1 resulted in increased grain width and weight, whereas overexpression of FGW1 led to slightly narrower kernels and better grain filling. In a yeast two-hybrid assay, FGW1 interacted directly with the 14–3–3 protein GF14f, bimolecular fluorescence complementation verified that the site of interaction was the membrane, and the mutated FGW1 protein failed to interact with GF14f. The expression of GF14f was down-regulated in fgw1, and the activities of AGPase, StSase, and SuSase in the endosperm of fgw1 increased similarly to those of a reported GF14f-RNAi. Transcriptome analysis indicated that FGW1 also regulates cellular processes and carbohydrate metabolism. Thus, FGW1 regulated grain formation via the GF14f pathway.