Ishizaki Takuma, Ueda Yoshiaki, Takai Toshiyuki, Maruyama Kyonoshin, Tsujimoto Yasuhiro
Tropical Agriculture Research Front, Japan International Research Center for Agricultural Sciences (JIRCAS), Ishigaki, Okinawa 907-0002, Japan.
Crop, Livestock and Environment Division, JIRCAS, Tsukuba, Ibaraki 305-8686, Japan.
Plant Sci. 2023 May;330:111627. doi: 10.1016/j.plantsci.2023.111627. Epub 2023 Feb 1.
Tillering is an important trait in rice productivity. We introduced mutations into the coding region of rice TEOSINTE BRANCHED1 (OsTB1), which is a negative regulator of tillering, using CRISPR/Cas9. The frameshift mutants exhibited substantially enhanced tillering and produced 3.5 times more panicles than the non-mutated plants at maturity. This enhanced tillering resulted in increased spikelet number; however, grain yields did not increase due to substantially reduced filled grain rate and 1,000-grain weight. In contrast, in-frame mutations in OsTB1 had the effect of slightly increasing tiller numbers, and the in-frame mutants had 40% more panicles than non-mutated plants. The grain yield of in-frame mutants also did not increase on nutrient-rich soil; however, under phosphorus-deficient conditions, where tillering is constrained, the in-frame mutants gave a significantly higher grain yield than non-mutated plants due to higher spikelet number and maintained filled grain rate. Rice grassy tiller1 (OsGT1)/OsHox12, which is directly regulated by OsTB1 to suppress tillering, was moderately down-regulated in in-frame mutants, suggesting that OsTB1 with the in-frame mutation shows partial function of intact OsTB1 in regulating OsGT1/OsHox12. We propose that mildly enhanced tillering by in-frame mutation of OsTB1 can improve grain yield under low phosphorus conditions.
分蘖是水稻产量的一个重要性状。我们利用CRISPR/Cas9技术，在水稻分蘖负调控因子TEOSINTE BRANCHED1（OsTB1）的编码区引入突变。移码突变体表现出显著增强的分蘖能力，成熟时产生的穗数是非突变植株的3.5倍。这种增强的分蘖导致小穗数增加；然而，由于饱满粒率和千粒重大幅降低，籽粒产量并未增加。相比之下，OsTB1的框内突变具有略微增加分蘖数的作用，框内突变体的穗数比非突变植株多40%。在营养丰富的土壤上，框内突变体的籽粒产量也没有增加；然而，在缺磷条件下，分蘖受到限制，框内突变体由于小穗数增加和饱满粒率维持不变，籽粒产量显著高于非突变植株。受OsTB1直接调控以抑制分蘖的水稻丛生分蘖1（OsGT1）/OsHox12在框内突变体中适度下调，这表明具有框内突变的OsTB1在调控OsGT1/OsHox12方面表现出完整OsTB1的部分功能。我们提出，通过OsTB1的框内突变适度增强分蘖可以在低磷条件下提高籽粒产量。
