Natural allelic variation of GmST05 controlling seed size and quality in soybean.

Seed size is one of the most important agronomic traits determining the yield of crops. Cloning the key genes controlling seed size and pyramiding their elite alleles will facilitate yield improvement. To date, few genes controlling seed size have been identified in soybean, a major crop that provides half of the plant oil and one quarter of the plant protein globally. Here, through a genome-wide association study of over 1800 soybean accessions, we determined that natural allelic variation at GmST05 (Seed Thickness 05) predominantly controlled seed thickness and size in soybean germplasm. Further analyses suggested that the two major haplotypes of GmST05 differed significantly at the transcriptional level. Transgenic experiments demonstrated that GmST05 positively regulated seed size and influenced oil and protein contents, possibly by regulating the transcription of GmSWEET10a. Population genetic diversity analysis suggested that allelic variations of GmST05 were selected during geographical differentiation but have not been fixed. In summary, natural variation in GmST05 determines transcription levels and influences seed size and quality in soybean, making it an important gene resource for soybean molecular breeding.

Indel marker analysis of putative stress-related genes reveals genetic diversity and differentiation of rice landraces in peninsular Thailand.

Genetic assessment of rice landraces is important for germplasm evaluation and genetic resource utilization. Rice landraces in peninsular Thailand have adapted to unique environmental stresses over time and have great significance as a genetic resource for crop improvement. In this study, rice landraces derived from rice research centers and farmers from different areas of peninsular Thailand were genetically assessed using 16 polymorphic InDel markers from putative stress-related genes. A total of 36 alleles were obtained. The average PIC value was 0.27/marker. The FST varied from 0.46 to 1.00. Genetic diversity was observed both within and between populations. AMOVA indicated that genetic variations occurred mainly between populations (70%) rather than within populations (30%). The dendrogram, population structure, and PCoA scatter plot clearly demonstrated the differentiation of the two major groups, i.e., landraces from upland and lowland rice ecosystems. The unique alleles of Indel1922, -2543, -6746, -7447 and -8538, which lie in genes encoding putative WAX2, heavy metal-associated domain-containing protein, GA20ox2, PTF1, and PLETHORA2, respectively, were only found in rice from upland ecosystems. Putative WAX2, GA20ox2, and PLETHORA2 are likely related to drought and salt stress. Our findings demonstrate the diversity of landraces in peninsular Thailand. The preservation of these landraces should be facilitated with effective markers to maintain all variant alleles and to protect the genetic diversity. Indel1922, -2543, -6746, -7447 and -8538 have the potential to differentiate upland rice from lowland rice. Furthermore, Indel1922, -6746 and -8538 might be effective markers for drought and salt tolerance.

Genetic interactions between diverged alleles of Early heading date 1 (Ehd1) and Heading date 3a (Hd3a)/ RICE FLOWERING LOCUS T1 (RFT1) control differential heading and contribute to regional adaptation in rice (Oryza sativa).

Initiation of flowering, also called heading, in rice (Oryza sativa) is determined by the florigens encoded by Heading date 3a (Hd3a) and RICE FLOWERING LOCUS T1 (RFT1). Early heading date 1 (Ehd1) regulates Hd3a and RFT1. However, different rice varieties have diverged alleles of Ehd1 and Hd3a/RFT1 and their genetic interactions remain largely unclear. Here we generated three segregating populations for different combinations of diverged Ehd1 and Hd3a/RFT1 alleles, and analyzed their genetic interactions between these alleles. We demonstrated that, in an ehd1 mutant background, Hd3a was silenced, but RFT1 was expressed (although at lower levels than in plants with a functional Ehd1) under short-day (SD) and long-day (LD) conditions. We identified a nonfunctional RFT1 allele (rft1); the lines carrying homozygous ehd1 and Hd3a/rft1 failed to induce the floral transition under SD and LD conditions. Like Hd3a, RFT1 also interacted with 14-3-3 proteins, the florigen receptors, but a nonfunctional RFT1 with a crucial E105K mutation failed to interact with 14-3-3 proteins. Furthermore, analyses of sequence variation and geographic distribution suggested that functional RFT1 alleles were selected during rice adaptation to high-latitude regions. Our results demonstrate the important roles of RFT1 in rice flowering and regional adaptation.