The TIP4;3
Hap2 allele improves cold tolerance in maize. (a) Chilling phenotypes of near‐isogenic lines (NILs) carrying the allele conferring cold tolerance (TIP4;3
Hap2) or the allele conferring cold sensitivity (TIP4;3
Hap1). (b) Leaf injury area of the NILs when exposed to cold stress. Bars represent 10 seedlings for each genotype in three independent experiments. Different letters represent significant differences (P < 0.05) determined by one‐way ANOVA with Tukey's multiple comparisons test. (c) Relative TIP4;3 expression levels in NIL‐Hap1 (TIP4;3 allele from 4019) and NIL‐Hap2 (TIP4;3 allele from 384‐2). Total RNA was extracted from three seedlings in each independent experiment. Different letters represent significant differences (P < 0.05) determined by one‐way ANOVA with Tukey's multiple comparisons test. (d–f) Chilling phenotypes (d), leaf injury area (e), and ion leakage (f) of WT and tip4;3 mutants. Fourteen‐day‐old seedlings grown at 25 °C were exposed to 4 °C for 3 days. Representative images were taken after 2 days of recovery at 25 °C. (g, h) Germination rates of WT, TIP4;3‐OE lines and tip4;3 mutants at 25 °C (g) or 12 °C For each assay, 30 seeds of WT, TIP4;3‐OE lines and tip4;3 mutants were placed in an incubator at 25 °C and 12 °C after soaking in water for 24 h. (i, j) Daily average minimum and maximum temperatures (i) and germination rates of WT, TIP4;3‐OE and tip4;3 mutants in natural field conditions (j). Seeds were sown on April 8, with 30 seeds per pot; the germination rate was scored over 14 consecutive days. The daily minimum temperature was 5 °C, and the maximum temperature was 27 °C. Error bars represent mean ± SD (standard deviation) from 3 biological replicates. *P < 0.05, **P < 0.01, *** P < 0.001, Student's two‐sided t‐test.