The floral organs are formed from floral meristem with a regular initiation pattern in angiosperm species. Flowers of naked seed rice (nsr) were characterized by the overdeveloped lemma and palea, the transformation of lodicules to palea-/lemma-like organs, the decreased number of stamens and occasionally extra pistils. Some nsr spikelets contained additional floral organs of four whorls and/or abnormal internal florets. The floral primordium of nsr spikelet is differentiated under an irregular pattern and an incomplete determination. And molecular analysis indicated that nsr was a novel homeotic mutation in OsMADS1, suggesting that OsMADS1 played a distinct role in regulating the differentiation pattern of floral primordium and in conferring the determination of flower meristem. The gain-of-function of OsMADS1 transgenic lines presented the transformation of outer glumes to lemma-/ palea-like organs and no changes in length of lemma and palea, but loss-of-function of OsMADS1 transgenic lines displayed the overdeveloped lemma and palea. Both findings revealed that OsMADS1 played a role in specifying lemma and palea and acted as a repressor of overdevelopment of lemma and palea. Moreover, it was indicated that OsMADS1 upregulated the transcript level of AP3 homologue OsMADS16, using real-time PCR analysis on gain- and loss-of-function of Os- MADS1 transgenic lines.

Using a newly developed mapping model with endosperm and maternal main effects and QTL environment interaction effects on quantitative quality traits of seed in cereal crops, the investigation of quantitative trait loci (QTLs) located on triploid endosperm and diploid maternal plant genomes for protein content and lysine content of rice grain under different environments was carried out with two backcross (BC1F1 and BC2F1) populations from a set of 241 recombinant inbred lines derived from an elite hybrid cross of Shanyou 63. The results showed a total of 18 QTLs to be associated with these two quality traits of rice, which were subsequently mapped on chromosomes 2, 3, 5, 6, 7, 10, 11 and 12. Three of these QTLs were also found havingQTL environment interaction effects. Therefore, the genetic main effects from QTLs located on chromosomes in endosperm and maternal plant genomes and their QTL environment interaction effects in different environments were all important for protein and lysine contents in rice. The influence of environmental factors on the expression of some QTLs located in different genetic systems could not be ignored for both nutrient quality traits.

It is necessary for rice breeders to understand the genetic basis of nutrient quality traits of rice. Essential amino acids are most important in determining the nutrient quality of rice grain and can affect the health of people who depend on rice as a staple food. In view of the paucity of genetic information available on essential amino acids in indica rice, we estimated the genetic main effects and genotype×environment (G×E) interaction effects on the content of essential amino acids. Nine cytoplasmic male sterile lines as females and five restorer lines as males were introduced in a North Carolina Ⅱ design across environments. Estimates of the content of the essential amino acids valine, methionine, leucine and phenylalanine showed that they were mainly controlled by genetic main effects, while the contents of threonine, cysteine and isoleucine were mainly affected by G×E effects. In the case of genetic main effects, both cytoplasmic and maternal genetic effects were predominant for all essential amino acids, indicating that selection for improving essential amino acid content based on maternal performance would be more effective than that based on seeds. The total narrow-sense heritabilities were high and ranged from 0.72 to 0.83. Since general heritabilities for these essential amino acids (except for cysteine) were found to be much larger than G×E interaction heritability, the improvement of content of most essential amino acids under selection would be expected under various environments.

A seed genetic model with embryo, endosperm, cytoplasmic and maternal effects and genotype