Seed germination, which initiates the plant life cycle, exhibits high sensitivity to salt stress, a significant environmental factor limiting rice production.  Brassinosteroid (BR), a growth-promoting phytohormone, mitigates various stresses including salt, drought, and extreme temperatures in rice.  However, the mechanisms by which BR alleviates salt stress during seed germination remain inadequately characterized.  This study demonstrates that seed-specific overexpression of OsDWF4, a rate-limiting gene in BR biosynthesis, enhances rice germination.  The DWF4-OX lines, which increase endogenous BR content in seeds, promote germination under salt stress, corroborating results obtained through exogenous BR application.  Antioxidant enzyme analyses demonstrate that BR enhances the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT).  Metabolomic analysis reveals that BR mitigates salt stress primarily through the biosynthesis of phenylpropanoids and secondary metabolites.  Transcriptomic analysis indicates that both endogenous and exogenous BR share five co-regulated target genes and utilize a common biosynthetic pathway for stilbenoids, diarylheptanoids, and gingerols.  These findings confirm BR's capacity to enhance seed germination under salt stress and identify several BR-mediated targets for developing salt-tolerant rice varieties suitable for direct seeding cultivation.

The female inflorescence, or ear, of maize develops no branch meristem (BM), which differs from the male inflorescence, or tassel.  While the mutations of some well documented genes, such as fea2/3/4 and ramosa1/2/3, can cause the branched architecture of ears in maize, such mutations also change the normal phenotypic performance of the tassels.  In the present study, a natural maize mutant with branched ears, named branched ear1 (be1), was characterized.  be1 shows several branched ears at the base of the central ear with unchanged architecture of the tassels.  Besides, both the branched and central ears of be1 possess regularly arranged kerels.  The phenotypic characteristics of be1 differ completely from those reported mutants of fasciated ears or RAMOSA-like ears in maize.  An SEM survey at the very early development stage showed that meristems with three protrusions, similar to the BM in tassels, were present during the development of the branched ears in be1.  Gene mapping and sequence alignment suggested that TEOSINTE BRANCHED1 (TB1) was the candidate gene of BE1.  Further verification showed that a be1-specific 31 bp deletion at the downstream of BE1 led to statistically reduced expression of this gene in the immature ear, which serves as the potential causal reason for the branched ears of be1.  CRISPR/Cas9-based gene editing downstream of TB1 complemented the phenotypic architecture of branched ears, suggesting that TB1 was the target of BE1, and it was named as ZmTB1^be1.  The results of the present study implied a novel function of TB1 in female inflorescence development, rather than shaping the plant architecture in maize.  Meanwhile, further functional dissection of ZmTB1^be1 might shed new light on TB1, the most famous domestication related gene in maize.

Potassium (K) improves the grain yield and stress resistance of crops; however, its effect on rice under shading stress is unclear.  In this study, a two-factor split-plot experiment was conducted in Sichuan, China, to evaluate the influence of K management methods on the morphological and physiological characteristics of leaves and grain yield under shading stress.  The results showed that leaf morphological and physiological traits had a greater relationship with grain yield under shading stress than under full sunlight.  Compared to full sunlight control, shading stress significantly increased the leaf area index (LAI) by improving the green leaf number and leaf area of rice.  Shading stress also significantly increased the chlorophyll, K⁺, and Na⁺ contents, but decreased the specific leaf weight, ratios of grain-to-leaf area and chlorophyll a/b, net photosynthetic rate (P_n), and sucrose and starch contents.  This resulted in a 16.21–29.71% reduction in grain yield by reducing the seed setting rate and 1,000-grain weight.  Compared to the no potassium application control (K_0-0), the green leaf number and leaf area of rice were significantly increased by K fertilizer, resulting in 15.61–29.88% and 13.46–22.20% increases in the total LAI under full sunlight control and shading stress, respectively.  K fertilizer significantly improved the chlorophyll b, K⁺, and K⁺/Na⁺ contents, but decreased the chlorophyll a/b ratio under shading stress, thereby enhancing P_n and increasing the sucrose and starch contents of flag leaves.  Therefore, K fertilizer significantly increased the grain yield by 5.57–17.35% under shading stress.  Compared to 90 kg ha^-1 of K₂O single use as basal fertilizer (K_90-0), 90 kg ha^-1 of K₂O single use as panicle fertilizer at panicle initiation stage (K_0-90) significantly increased the P_n and starch content of flag leaves under shading stress.  Furthermore, there was no significant difference between the grain yields of K_0-90 and 180 kg ha^-1 of K₂O equal-spilt applicated as basal and panicle fertilizers (K_90-90) in 2021 (except under shading stress) and 2022.  Overall, K fertilizer, particularly panicle K, improved the LAI and photosynthetic performance of rice, resulting in an improved rice grain yield under shading stress.