Five Rice Seed-Specific NF-YC Genes Redundantly Regulate Grain Quality and Seed Germination via Interfering Gibberellin Pathway.

NF-YCs are important transcription factors with diverse functions in the plant kingdoms including seed development. NF-YC8, 9, 10, 11 and 12 are close homologs with similar seed-specific expression patterns. Despite the fact that some of the NF-YCs are functionally known; their biological roles have not been systematically explored yet, given the potential functional redundancy. In this study, we generated pentuple mutant pnfyc of NF-YC8-12 and revealed their functions in the regulation of grain quality and seed germination. pnfyc grains displayed significantly more chalkiness with abnormal starch granule packaging. pnfyc seed germination and post-germination growth are much slower than the wild-type NIP, largely owing to the GA-deficiency as exogenous GA was able to fully recover the germination phenotype. The RNA-seq experiment identified a total of 469 differentially expressed genes, and several GA-, ABA- and grain quality control-related genes might be transcriptionally regulated by the five NF-YCs, as revealed by qRT-PCR analysis. The results demonstrated the redundant functions of NF-YC8-12 in regulating GA pathways that underpin rice grain quality and seed germination, and shed a novel light on the functions of the seed-specific NF-YCs.

Cyclin-Dependent Kinase Inhibitors KRP1 and KRP2 Are Involved in Grain Filling and Seed Germination in Rice (Oryza sativa L.).

Cyclin-dependent kinase inhibitors known as KRPs (kip-related proteins) control the progression of plant cell cycles and modulate various plant developmental processes. However, the function of KRPs in rice remains largely unknown. In this study, two rice KRPs members, KRP1 and KRP2, were found to be predominantly expressed in developing seeds and were significantly induced by exogenous abscisic acid (ABA) and Brassinosteroid (BR) applications. Sub-cellular localization experiments showed that KRP1 was mainly localized in the nucleus of rice protoplasts. KRP1 overexpression transgenic lines (OxKRP1), krp2 single mutant (crkrp2), and krp1/krp2 double mutant (crkrp1/krp2) all exhibited significantly smaller seed width, seed length, and reduced grain weight, with impaired seed germination and retarded early seedling growth, suggesting that disturbing the normal steady state of KRP1 or KRP2 blocks seed development partly through inhibiting cell proliferation and enlargement during grain filling and seed germination. Furthermore, two cyclin-dependent protein kinases, CDKC;2 and CDKF;3, could interact with KRP1 in a yeast-two-hybrid system, indicating that KRP1 might regulate the mitosis cell cycle and endoreduplication through the two targets. In a word, this study shed novel insights into the regulatory roles of KRPs in rice seed maturation and germination.

Construction of a Quantitative Acetylomic Tissue Atlas in Rice (Oryza sativa L.).

PKA (protein lysine acetylation) is a key post-translational modification involved in the regulation of various biological processes in rice. So far, rice acetylome data is very limited due to the highly-dynamic pattern of protein expression and PKA modification. In this study, we performed a comprehensive quantitative acetylome profile on four typical rice tissues, i.e., the callus, root, leaf, and panicle, by using a mass spectrometry (MS)-based, label-free approach. The identification of 1536 acetylsites on 1454 acetylpeptides from 890 acetylproteins represented one of the largest acetylome datasets on rice. A total of 1445 peptides on 887 proteins were differentially acetylated, and are extensively involved in protein translation, chloroplast development, and photosynthesis, flowering and pollen fertility, and root meristem activity, indicating the important roles of PKA in rice tissue development and functions. The current study provides an overall view of the acetylation events in rice tissues, as well as clues to reveal the function of PKA proteins in physiologically-relevant tissues.

Genome-Wide Identification of lncRNAs During Rice Seed Development.

Rice seed is a pivotal reproductive organ that directly determines yield and quality. Long non-coding RNAs (lncRNAs) have been recognized as key regulators in plant development, but the roles of lncRNAs in rice seed development remain unclear. In this study, we performed a paired-end RNA sequencing in samples of rice pistils and seeds at three and seven days after pollination (DAP) respectively. A total of 540 lncRNAs were obtained, among which 482 lncRNAs had significantly different expression patterns during seed development. Results from semi-qPCR conducted on 15 randomly selected differentially expressed lncRNAs suggested high reliability of the transcriptomic data. RNA interference of TCONS_00023703, which is predominantly transcribed in developing seeds, significantly reduced grain length and thousand-grain weight. These results expanded the dataset of lncRNA in rice and enhanced our understanding of the biological functions of lncRNAs in rice seed development.