IC4R006-miRNA-2014-25052585

Project Title

Differentially expressed microRNA cohorts in seed development may contribute to poor grain filling of inferior spikelets in rice

The Background of This Project

[[File:|700px|thumb|right|Figure 1. GWA Analysis of Al Tolerance within and across Rice Subpopulations.]]

• The inferior spikelets are defined to be those at portions where the grains receive less photosynthetic products during the seed development. The typical inferior spikelets are physically located on the proximal secondary branches in a rice panicle and traditionally characterized by a later flowering time and a slower grain-filling rate, compared to those so-called superior spikelets. Grains produced on the inferior spikelets are consequently under-developed and lighter in weight than those formed on the superior spikelets. MicroRNAs (miRNAs) are recognized as key players in regulating plant development through post-transcriptional gene regulations. We previously presented the evidence that miRNAs may influence grain-filling rate and played a role in determining the grain weight and yield in rice.
• Rice (Oryza sativa L.) is one of the most important food crops in the world, providing calories for over 21% of global population and 76% of South East Asian. The yield of rice is determined primarily by two vital factors, the grain filling rate and subsequently the grain weight. It has been demonstrated by many researches that grain weight and the grain plumpness (a parameter describing the grain quality) are mostly positional-dependent in a rice panicle. A rice panicle is composed of numerous branches termed spikelets with some having high quality seeds termed superior spikelets and some with poor quality seeds termed inferior spikelets. In general, the superior spikelets flower earlier and subse- quently have a faster grain-filling rate in seed development, producing high-quality seeds. The flowers or seeds on superior spikelets are typically located on apical primary branches in a panicle. In contrast, the inferior spikelets flower later with a lower grain-filling rate and are located on the proximal secondary branches, resulting in low-quality seeds.
• MicroRNAs (miRNAs), a type of endogenous non-coding small RNAs produced from stem-loop structured precursors, have been proved to play curial roles in many aspects of plant development, such as organ morphogenesis, stress response, flowering control, phytohormone homeostasis, and grain/fruit development. The expressions of various miRNAs are extremely dynamic during rice grain development, revealed by a series of studies utilizing small RNA high-throughput sequencing technology. For example, in one study, most miRNAs were shown to be equally expressed or expressed much higher in grains of 6–10 days than those of 1–5 days after fertilization. A similar study showed that a high proportion of the detected miRNAs were up-regulated in seeds of 5 to 7 days after fertilization. The analysis of 445 known miRNAs and 45 novel miRNAs in our previous studies suggests the expressions of these miRNAs in rice grain were in a developmental stage dependent manner. The expressions of most known miRNAs increased gradually as rice grain filling went on [16]. These observations were also in contrast to another study showing that about half of the known miRNAs were up-regulated, while the remaining miRNAs were down-regulated during indica rice grain development.

Research Findings

[[File:|700px|thumb|right|Figure 2. Haplotype analysis of the Nrat1 gene region.]]

Labs working on this Project

• Collaborative Innovation Center of Henan Grain Crops, Henan Agricultural University, Zhengzhou 450002, China
• Research Center for Rice Engineering in Henan Province, Henan Agricultural University, Zhengzhou 450002, China

Corresponding Author

• Quanzhi Zhao (qzzhaoh@126.com)