Sweet Sorghum Originated through Selection of Dry, a Plant-Specific NAC Transcription Factor Gene.

Sorghum (Sorghum bicolor) is the fifth most popular crop worldwide and a C4 model plant. Domesticated sorghum comes in many forms, including sweet cultivars with juicy stems and grain sorghum with dry, pithy stems at maturity. The Dry locus, which controls the pithy/juicy stem trait, was discovered over a century ago. Here, we found that Dry gene encodes a plant-specific NAC transcription factor. Dry was either deleted or acquired loss-of-function mutations in sweet sorghum, resulting in cell collapse and altered secondary cell wall composition in the stem. Twenty-three Dry ancestral haplotypes, all with dry, pithy stems, were found among wild sorghum and wild sorghum relatives. Two of the haplotypes were detected in domesticated landraces, with four additional dry haplotypes with juicy stems detected in improved lines. These results imply that selection for Dry gene mutations was a major step leading to the origin of sweet sorghum. The Dry gene is conserved in major cereals; fine-tuning its regulatory network could provide a molecular tool to control crop stem texture.

[Effects of high temperature and hydrogen cyanamide on dormant nectarine's floral bud respiratory metabolism].

Taking 3-year old potted 'Shuguang' nectarine (Prunus persica var. nectariana cv. Shuguang) as test material, this paper studied the effects of high temperature (50 degrees C, HT) and hydrogen cyanamide (HC) on the floral bud respiratory metabolism of the tree during its natural dormancy. Both HT and HC could break the natural dormancy of the tree, and lead to a significant decrease in the respiratory metabolism of floral buds for several hours. The main respiratory pathways, tricarboxylic acid cycle (TCA) and pentose phosphate pathway (PPP), were affected. For the buds not received dormancy-breaking treatments, both the TCA and the PPP decreased, while treating with HT and HC induced a rapid recovery of PPP after the early respiratory attenuation. HT also induced the recovery of TCA, but HC did not show this effect in 96 hours. Therefore, respiratory attenuation and the following PPP activation could be the important part in the floral bud respiratory mechanism of HT- and HC-induced dormancy release.

[Transcriptional levels of AQPs genes in peach floral buds during dormancy].

Taking the floral buds of 10 years old field-cultivated and 3 years old potted nectarine (Prunus persica var. nectarine cv. Shuguang) as test materials, and by the method of real-time quantitative PCR, this paper studied the expressions of the AQPs genes deltaTIP1 and PIP1; 1 during dormancy and dormancy-release (September 15, 2009-January 15, 2010) and the transcriptional levels of the genes under low temperature stress. Within the period of dormancy and dormancy-release, the transcriptional level of PIP1; 1 presented a persistent increasing trend, and the high level expression of PIP1; 1 in January could be related to the efflux of water through cytoplasma membrane and vacuolar membrane, which protected the bud cells from ice crystal injuries. The contents of soluble sugar, soluble protein, and proline in the bud cells all peaked in January, which prevented the excessive water loss from the cells. After 2 weeks of low temperature treatment, the PIP1; 1 had a high level expression, indicating that it was a cold-induced gene. The transcriptional level of deltaTIP1 fluctuated during dormancy, and increased significantly during dormancy-release, which might be induced by the dormancy-release signals in buds and the resumption of plant activity. After 2 weeks of low temperature treatment, the expression level of deltaTIP1 had no increase, indicating that deltaTIP1 was not a cold-induced gene.