Development of Soft Rice Lines by Regulating Amylose Content via Editing the 5′UTR of the Wx Gene

Abstract

The type of soft rice with low amylose content (AC) is more and more favored by consumers for its better eating and cooking quality, as people’s quality of life continuously improves in China. The Wx gene regulates the AC of rice grains, thus affecting the degree of softness of the rice. Mei Meng B (MMB), Tian Kang B (TKB), and DR462 are three indica rice maintained lines with good morphological characters, but also with undesirably high AC. Therefore, CRISPR/Cas9 technology was used to edit the Wx gene of these lines to create a batch of soft rice breeding materials. New gene-edited lines MMB-10-2, TKB-21-12, and DR462-9-9, derived from the above parental lines, respectively, were selected in the T2 generations, with an AC of 17.2%, 16.8%, and 17.8%, and gel consistency (GC) of 78.6 mm, 77.4 mm, and 79.6 mm, respectively. The rapid viscosity analysis (RVA) spectrum showed that the three edited lines had a better eating quality as compared to the corresponding wild type, and showing new characteristics, different from the high-quality soft rice popular in the market. There was no significant difference in the main agronomic traits in the three edited lines compared to the corresponding wild types. Moreover, the chalkiness of DR462-9-9 was reduced, resulting in an improved appearance of its polished rice. The present study created soft rice germplasms for breeding improved quality hybrid rice, without changing the excellent traits of their corresponding wild type varieties.

Molecular and genetic bases of rice cooking and eating quality: An updated review

“…A high‐to‐low AAC selection trend in the course of rice domestication (Zhang et al, 2019) and in current global rice breeding programs is prevalent, since low‐amylose rice or soft rice has become increasingly more popular (Calingacion et al, 2014; Yang et al, 2022; Zhou et al, 2022). In current rice breeding programs, the major Wx alleles in modern cultivated rice are Wx a , Wx b , and Wx in (Zhang et al, 2019).…”

“…However, editing conserved cis‐acting elements in the promoter of the Wx gene may reduce Wx expression levels, resulting in a lower AAC and improvement of CEQ. Some novel Wx alleles with reduced amylose levels by promoter editing using the CRISPR/Cas9 system have been successfully obtained in rice either carrying the Wx b allele (Huang et al, 2020) or the Wx a allele (Yang et al, 2022; Zeng et al, 2020). Targeting of these sequences is useful for CEQ improvement via modification of expression of the Wx gene.…”

Molecular Research for Cereal Grain Quality

“…However, due to increases in the human population and urbanization and a decline in arable land, the higher production demand remains challenging for many nations. On the other hand, with the increase in living standards thanks to economic development, our desire for a better life requires more production of high-quality cereal foods [ 1 , 2 ].…”

“…This Special Issue aims to provide a forum on the most recent advances in the application of molecular tools to understand the mechanism for improving any cereals’ grain quality. A total of 13 papers were collected for this Special Issue [ 1 , 2 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], mainly covering rice and wheat crops.…”

“…CRISPR/Cas9 technology was used to edit the 5′ UTR of the Wx gene of three lines with undesirably high AAC to create a batch of soft rice (low-AAC rice) breeding materials. The edited rice lines had an AAC of 16–18% and gel consistency of 77–80 mm, suggesting that the eating quality was successfully improved [ 2 ]. Lu et al [ 6 ] obtained a high-quality chromosome-level genome assembly (~378.78 Mb) for a new fragrant japonica cultivar “Changxianggeng 1813”, with 31,671 predicted protein-coding genes.…”