Boron deficiency alters root growth and development and interacts with auxin metabolism by influencing the expression of auxin synthesis and transport genes

Figures & data

Table 1. Gene IDs and specific primers for quantitative real-time PCR analysis.

Gene	Accession no.	Function classification	Forward primer (5′–3′)	Reverse primer (5′–3′)	Amplicon size (bp)
ABCB1	Ciclev10010916m	Auxin carrier	GAGCCATTCACGCCACTTC	TCTTGTAACCGAGCCTTTGAGC	186
ABCB19	Ciclev10010931m	Auxin carrier	GCATGAGTTTGGGTCAGTCTTT	CATCTTCCATTTGTTGGGTCTT	127
AUX1	Ciclev10011596m	Auxin carrier	CTTGACTCTGCCCTATTCATTCTC	TGGACCCAGTAACCCATCAAGC	205
LAX1	Ciclev10031413m	Auxin carrier	TTGGCGGACATGCAGTGAC	CAGCGGCAGCAGAAGGAAT	123
LAX2	Ciclev10028271m	Auxin carrier	TGTGGGAAGATGGGTAGGGAC	TAGTCATGCTCGCCCACCC	98
LAX3	Ciclev10001072m	Auxin carrier	ATCACTTTCGCTCCTGCTGC	CAAACCCAAATCCCACCACTA	133
PIN1	Ciclev10007787m	Auxin carrier	GCTTTGGCAACAGAAGAGGATT	ATTACACTTGTCGGCGGCATA	94
PIN3	orange1.1g006199m	Auxin carrier	CATGCCTCCAGCGAGTGTTAT	TGCCACCTGAAAGCGATTAGA	126
PIN4	Ciclev10012938m	Auxin carrier	ATGGGGTTGAAAACGAAGGG	CCTGATAAGTTTCCTCCACACCA	167
TAA1	Ciclev10033774m	IAA synthesis	TTTGAGGCGTTTTGGAGGAA	TTGTTGATTGCTTCAGCGAGTT	134
TAR2	Ciclev10020085m	IAA synthesis	CACACACGGCACACCCCTA	GCCTCCCACTCCCCAGATC	137
YUC2	Ciclev10027059m	IAA synthesis	CAGTGTGGCTGTTGAAATGGTT	CCATCATCTAGGACTGGGGTTT	166
YUC3	Ciclev10006828m	IAA synthesis	CCTTCAGGTTTAGCCGTTGC	GGAAGTTTGGAAGTTGGCAGA	157
YUC4	Ciclev10008466m	IAA synthesis	GACCATCTGGGTTAGCCGTTT	GTATTTTGGGAAGTTTTCAGGGA	185
YUC6	Ciclev10008473m	IAA synthesis	GTGGTTGCTAAAGTGGCTGC	GTTGAAGGGGACCCAAAAGA	122
YUC8	Ciclev10020503m	IAA synthesis	GTGATAATGGTAGGGGCAGGA	GAATGGCAGGTGAGGGAGC	183
β-actin	Ciclev10025866m	Reference gene	CCGACCGTATGAGCAAGGAAA	TTCCTGTGGACAATGGATGGA	190

Figure 1. Morphological and anatomical symptoms in trifoliate orange roots cultivated hydroponically under +B (0.25 mg L⁻¹ boron) or −B (∼0.25 µg L⁻¹ boron) conditions for eight weeks. Morphological symptoms of the whole roots (a) and a single root (b); longitudinal sections of root tips cultivated under +B conditions (c); different longitudinal sections of root tips cultivated under –B conditions (d, e).

Table 2. Effects of boron deficiency on the root morphology of trifoliate orange seedlings after 8-week hydroponic cultivation.

Treatment	Root number	Total root length (cm)	Root density (no./cm)
+B (0.25 mg L^−1)	44.15 ± 6.52^a	101.12 ± 8.99^a	0.44 ± 0.07^a
–B (∼0.25 µg L^−1)	38.70 ± 7.23^a	53.03 ± 9.43^b	0.74 ± 0.15^b

Note: Data are presented as means with standard error of the mean (± SEM) of three replicates (n = 3) with five plants each. Different lower-case letters in each column indicate significant differences (P < 0.05) between +B and -B treatments.

Figure 2. Effects of eight-week boron-deficiency treatment on the insoluble (isB) and soluble boron (sB) content (a) and IAA content (b) in trifoliate orange root tips.

Figure 3. Effects of a three-day boron-deficiency treatment on the insoluble boron (a), soluble boron (b) and IAA (c) content in trifoliate orange root tips.

Figure 4. Quantitative real-time PCR analysis of IAA biosynthesis genes in trifoliate orange root tips: TAA1 (a), TAR2 (b), YUC2 (c), YUC3 (d), YUC4 (e), YUC6 (f) and YUC8 (g).

Figure 5. Quantitative real-time PCR analysis of IAA transport genes in trifoliate orange root tips: ABCB1 (a), ABCB19 (b), AUX1 (c), LAX1 (d), LAX2 (e), LAX3 (f), PIN1 (g), PIN3 (h) and PIN4 (i).