Modified TAL expression in rice plant regulates yield components and grain quality in a N-rate dependent manner

Abstract

Context or problemHigher-yield and superior-quality rice are the major goals in rice breeding and nitrogen management. Genetic modification combined with optimal nitrogen (N) fertilization is expected to realize it. Objective or research questionModification in transaldolase (TAL) expression alters both the number and pattern of vascular bundles in rice plants, but its interactions with N rate remains unknown. MethodsWe employed three representative lines with different expression levels of TAL in the same genetic background (Wuyunjing 7, WT), and analyzed their responses in dry matter accumulation (DMA), carbohydrate transport, grain filling, yield, yield components, and grain quality under a wide range of N rate. ResultsIncreased expression of TAL (OE) promoted rice yield by producing more spikelets per panicle and higher 1000-grain weight, while decreased expression of TAL lowered the seed setting rate and grain weight significantly. Under a fixed N rate, when TAL expression was altered, the direct path coefficients of the seed setting rate and 1000-grain weight to the yield were higher than other yield components, especially at a high N rate. Decreased expression of TAL (RNAi) significantly reduced the starch and non-structural carbohydrates (NSC) contents in the stems, but enhanced the soluble sugar retention, whereas increased expression of TAL enhanced the translocation of NSC. The grain weight at maturity and mean grain-filling rate (mg d−1) increased significantly along with the TAL expression, but their differences among RNAi, WT and OE narrowed at higher N rate. Decreased expression of TAL enhanced the apparent amylose content (ACC) and protein (PC), reduced the starch granule size, and caused a loose starch arrangement and elevated chalkiness, as a consequence, significantly reduced the peak viscosity, hot viscosity, final viscosity, and taste value in a N rate dependent manner. The taste values of OE and WT were similar and the highest value was attained under a moderate N rate. ConclusionsTAL expression plays an important role in the regulation of assimilate supply, grain filling, yield formation, and grain quality. Increased expression of TAL alleviates competition effect among the yield components and enhances the yield potential, especially under moderate to high N rate. Higher TAL expression combined with a moderate N rate improves ECQ. Implications or significanceTAL expression and N rate interacts to regulate yield components and quality. This finding provides meaningful knowledge to administering N rate and genetically modifying TAL expression in a rice variety.