Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milan, Italy.
Plant Cell. 2012 Jul;24(7):2886-97. doi: 10.1105/tpc.112.100164. Epub 2012 Jul 10.
Hormones, such as auxin and cytokinin, are involved in the complex molecular network that regulates the coordinated development of plant organs. Genes controlling ovule patterning have been identified and studied in detail; however, the roles of auxin and cytokinin in ovule development are largely unknown. Here we show that key cytokinin pathway genes, such as isopentenyltransferase and cytokinin receptors, are expressed during ovule development. Also, in a cre1-12 ahk2-2 ahk3-3 triple mutant with severely reduced cytokinin perception, expression of the auxin efflux facilitator PIN-FORMED 1 (PIN1) was severely reduced. In sporocyteless/nozzle (spl/nzz) mutants, which show a similar phenotype to the cre1-12 ahk2-2 ahk3-3 triple mutant, PIN1 expression is also reduced. Treatment with the exogenous cytokinin N(6)-benzylaminopurine also altered both auxin distribution and patterning of the ovule; this process required the homeodomain transcription factor BELL1 (BEL1). Thus, this article shows that cytokinin regulates ovule development through the regulation of PIN1. Furthermore, the transcription factors BEL1 and SPL/NZZ, previously described as key regulators of ovule development, are needed for the auxin and cytokinin signaling pathways for the correct patterning of the ovule.
激素，如生长素和细胞分裂素，参与调节植物器官协调发育的复杂分子网络。控制胚珠模式形成的基因已被鉴定并进行了详细研究；然而，生长素和细胞分裂素在胚珠发育中的作用在很大程度上是未知的。在这里，我们表明关键的细胞分裂素途径基因，如异戊烯基转移酶和细胞分裂素受体，在胚珠发育过程中表达。此外，在 cre1-12 ahk2-2 ahk3-3 三重突变体中，细胞分裂素感知严重降低，生长素外排促进因子 PIN-FORMED 1 (PIN1) 的表达也严重降低。在 sporocyteless/nozzle (spl/nzz) 突变体中，也表现出与 cre1-12 ahk2-2 ahk3-3 三重突变体相似的表型，PIN1 的表达也降低。用外源细胞分裂素 N(6)-苄基腺嘌呤处理也改变了生长素的分布和胚珠的模式；这个过程需要同源域转录因子 BELL1 (BEL1)。因此，本文表明细胞分裂素通过调节 PIN1 来调节胚珠发育。此外，先前被描述为胚珠发育关键调节剂的转录因子 BEL1 和 SPL/NZZ，对于生长素和细胞分裂素信号通路正确模式化胚珠是必需的。
